Our verdict

During our lab evaluation, the StealthFit edition emerged as a remarkable variant of the regular Glycerin 21, showcasing a significant weight reduction and a snug, sock-like upper. Although it compromises somewhat on breathability and cushioning, we believe these trade-offs are justified for many runners. For us, this variant excels as a featherweight daily runner, impressing us with its comfort and durability across a variety of terrains.

zapatillas de running Brooks hombre media maratón Pros

  • Durable outsole
  • Sock-like tongue
  • Significant weight reduction
  • Comfortable fit
  • Great for long runs
  • Womens Brooks Method Perforated Running Biker Shorts
  • Supercritical foam

zapatillas de running Brooks hombre media maratón Cons

  • zapatillas de running Brooks pie cavo maratón rojas
  • Lacks energy return

Audience verdict

85
Good!
  • Brooks Beast 20 Беговая Обувь

Who should buy

We highly recommend the StealthFit variant of the Glycerin 21 for:

  • Fans of the classic Glycerin who desire a more secure, locked-in upper and a lighter overall build.
  • Marathoners looking for a durable, lightweight daily trainer that can handle extensive mileage with ease.
  • Those seeking a versatile workhorse with a knit, sock-like upper that's perfect for winter running.

zapatillas de running Brooks pie normal talla 43 blancas

Who should NOT buy

We do not recommend the Glycerin StealthFit 21 for those living in hot climates—the knit upper, while snug and comfortable, lacks sufficient ventilation and may lead to blisters and discomfort in warm weather. Instead, we suggest the Hoka Mach 6, which is far better suited for warmer conditions with its superior breathability.

Additionally, we think the Glycerin StealthFit 21 falls short in energy return compared to world-class daily trainers. If you're looking for a shoe with more bounce and an even lighter feel, we believe the ASICS Superblast is a better investment, offering greater energy return and an impressively low weight.

zapatillas de running Brooks pie normal talla 43 blancas parts

Cushioning

Heel stack

At the heel, we recorded a measurement of 36.9 mm, positioning the Glycerin StealthFit 21 as a high-stack model designed for extensive use.

This feature may not suit runners who prefer a closer connection to the ground. For them, we suggest the womens brooks run wild revel, Brooks Distance Graphic Mens T-shirt.

zapatillas de running Brooks pie normal talla 43 blancas Heel stack
Test results
Glycerin StealthFit 21 36.9 mm
Average 34.2 mm
Compared to 393 running shoes
tenis brooks ghost 13 azul vermelho preto
22.5 mm
Heel stack
46.3 mm

zapatillas de running Brooks hombre media maratón | Forefoot stack

The forefoot is also very cushioned (even by today's high standards) with a measurement of 26.4 mm from our digital calipers. This level of cushioning is more than adequate for long distances.

zapatillas de running Brooks pie normal talla 43 blancas Forefoot stack
Test results
Glycerin StealthFit 21 26.4 mm
Average 25.6 mm
Compared to 393 running shoes
tenis brooks ghost 13 azul vermelho preto
13.7 mm
Forefoot stack
37.1 mm

Drop

Brooks advertises a 10-mm heel-to-toe drop for the Glycerin StealthFit 21, and our thorough measurements confirmed it's nearly spot-on, showing a 10.5-mm offset.

This design makes the shoe particularly well-suited for heel strikers, though runners who utilize a forefoot or midfoot strike and prefer a higher offset can also enjoy them without any issues.

zapatillas de running Brooks pie normal talla 43 blancas Drop
Test results
Glycerin StealthFit 21 10.5 mm
Average 8.6 mm
Compared to 393 running shoes
tenis brooks ghost 13 azul vermelho preto
-0.2 mm
Drop
16.1 mm

Midsole softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

Fortunately, the enhanced DNA Loft v3 featured in the Glycerin 21 remains unchanged.

This nitrogen-infused EVA foam showed a 20.6 HA reading on our Shore A durometer. This measurement indicates a ride that perfectly balances firmness and plushness, offering a middle ground that, in our view, could appeal to a broad range of runners.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Midsole softness
Test results
Glycerin StealthFit 21 20.6 HA
Average 21.0 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 320 running shoes
tenis brooks ghost 13 azul vermelho preto
8.5 HA
Midsole softness (soft to firm)
35.0 HA

Midsole softness in cold (%)

After chilling the Glycerin 21 in the freezer for 20 minutes, we reassessed its softness with a durometer. Our findings indicated a significant letdown, as it increased its firmness by 36.9%. That's a bit too much, although it's a typical issue with EVA-based midsoles.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Difference in midsole softness in cold
Test results
Glycerin StealthFit 21 37%
Average 25%
Compared to 320 running shoes
tenis brooks ghost 13 azul vermelho preto
0%
Midsole softness in cold
63%

Insole thickness

The insole is consistent with other models in the Glycerin line, featuring a standard thickness of 5.2 mm.

zapatillas de running Brooks pie normal talla 43 blancas Insole thickness
Test results
Glycerin StealthFit 21 5.2 mm
Average 4.4 mm
Compared to 389 running shoes
tenis brooks ghost 13 azul vermelho preto
1.5 mm
Insole thickness
7.3 mm

Size and fit

Size

zapatillas de running Brooks pie normal talla 43 blancas is true to size (419 votes).

Owners of this shoe, how does this shoe fit?

1 size small ½ size small True to size ½ size large 1 size large
Compared to 367 running shoes
tenis brooks ghost 13 azul vermelho preto
½ size small
Slightly small
True to size
Slightly large
½ size large

Características Brooks england Alforja Scape 13L

Returning to the fit, which we previously noted as the key distinction between the StealthFit and the standard versions, our side-by-side tests of both shoes demonstrated a slightly tighter, more secure feel in this version.

To confirm our observations, we did a gel mold and found that the StealthFit version is narrower by 0.6 mm at 95.3 mm. Not so much!

zapatillas de running Brooks pie normal talla 43 blancas Características Brooks england Alforja Scape 13L
Test results
Glycerin StealthFit 21 95.3 mm
Average 95.5 mm
Compared to 148 running shoes
tenis brooks ghost 13 azul vermelho preto
88.5 mm
Características Brooks england Alforja Scape 13L
102.4 mm

Toebox width - big toe

The opposite trend seen in previous tests appears in the big toe area. Measuring 72.8 mm—1.1 mm wider than the standard version—this difference feels amplified by the material’s flexible properties, allowing enhanced comfort and adaptability when compared to the regular Glycerin.

zapatillas de running Brooks pie normal talla 43 blancas Toebox width - big toe
Test results
Glycerin StealthFit 21 72.8 mm
Average 73.7 mm
Compared to 148 running shoes
tenis brooks ghost 13 azul vermelho preto
67.9 mm
Toebox width - big toe
83.6 mm

Toebox height

From Boston to 8 Countries and Scored a Brooks Sponsorship.

This provides adequate space for most runners, though those craving extra upward toe freedom might favor other shoes with more space up front.

zapatillas de running Brooks pie normal talla 43 blancas Toebox height
Test results
Glycerin StealthFit 21 26.5 mm
Average 27.2 mm
Compared to 147 running shoes
tenis brooks ghost 13 azul vermelho preto
22.4 mm
Toebox height
33.8 mm

Stability

Lateral stability test

The StealthFit version shows slight variations in stability compared to the standard model, making it less supportive than its stability-oriented sibling, the Glycerin GTS 21. If support is crucial for your runs, the GTS 21 is the better choice, although it’s not available with a StealthFit upper. You’ll have to choose between one style or the other.

Nevertheless, this StealthFit edition offers a remarkably stable ride for any neutral runner. We believe that 99% of runners without stability issues should pick this one over the GTS.

Torsional rigidity

We found that the stable feel of this shoe is primarily attributed to its design dimensions, though the 3/5 rigidity we observed before also plays a significant role.

Fans of a traditional, natural ride may lean towards the standard version, which we found to be slightly more flexible (2/5) due to its upper construction.

Test results
Glycerin StealthFit 21 3
Average 3.4
Compared to 372 running shoes
tenis brooks ghost 13 azul vermelho preto
1
Torsional rigidity
5

Heel counter stiffness

The heel counter in the regular edition was a eyebrow-raising feature for us, as we found its super-stiff design a bit excessive for an average daily trainer.

However, the StealthFit version introduces a more thoughtful and accommodating design. From our testing, we found that this adjustment enhances comfort significantly for a daily trainer, earning it a balanced rating of 3/5 from our team.

Test results
Glycerin StealthFit 21 3
Average 2.9
Compared to 356 running shoes
tenis brooks ghost 13 azul vermelho preto
1
Heel counter stiffness
5

Midsole width - forefoot

zapatillas de running Brooks hombre media maratón daily running category. However, it doesn't reach the shares forefoot dimensions of the ASICS Novablast 4, which are similar to those found in maximalist stability shoes.

zapatillas de running Brooks pie normal talla 43 blancas Midsole width in the forefoot
Test results
Glycerin StealthFit 21 116.3 mm
Average 114.1 mm
Compared to 394 running shoes
tenis brooks ghost 13 azul vermelho preto
103.3 mm
Midsole width - forefoot
126.9 mm

Brooks Brothers Spodnie dresowe

Despite its notably high sole height in the heel, our neutral running technique remained impressively stable. This stability is greatly enhanced by the Glycerin StealthFit 21's exceptionally wide design—at a robust 99.1 mm—providing a secure landing platform for heel strikers.

We discovered that the generous width not only supports a solid base but also significantly boosts the shoe’s overall support. In our view, this broad design of the heel truly sets the StealthFit 21 apart in terms of stability versus other daily trainers.

zapatillas de running Brooks pie normal talla 43 blancas Midsole width in the heel
Test results
Glycerin StealthFit 21 99.1 mm
Average 90.7 mm
Compared to 394 running shoes
tenis brooks ghost 13 azul vermelho preto
73.0 mm
Brooks Brothers Spodnie dresowe
106.6 mm

zapatillas de running Brooks hombre constitución media ritmo bajo apoyo talón

While the shoe tends toward stiffness, strategically placed grooves in the outsole enhance its longitudinal flexibility, achieving a measure of 22.4N in our definitive 90-degree bend test.

zapatillas de running Brooks pie normal talla 43 blancas outsole flex

This adaptability is vital for the shoe to function as a dependable and versatile workhorse, comfortably handling multiple activities.

Test results
Glycerin StealthFit 21 22.4N
Average 28.2N
We use an average of four tests. The video shows one of those tests.
Compared to 376 running shoes
tenis brooks ghost 13 azul vermelho preto
2.2N
Flexibility <> Stiffness
72.1N

Brooks England Sillin B67 (%)

After chilling the Glycerin StealthFit 21 in the freezer for 20 minutes and retesting it with the force gauge, we found that it had increased it's stiffness by 17.4%.

Test results
Glycerin StealthFit 21 17%
Average 33%
Compared to 376 running shoes
tenis brooks ghost 13 azul vermelho preto
0%
Brooks England Sillin B67
111%

Weight

Choosing the StealthFit version brings a significant benefit—reduced weight. It trims 0.7 ounces off the regular v21, registering just 9.1 oz or 257g, which is remarkable for such a well-cushioned daily trainer.

The fact that this weight reduction is achieved solely through modifications to the upper, while maintaining or even enhancing comfort for some, is truly impressive.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Weight
Test results
Glycerin StealthFit 21 9.07 oz (257g)
Average 9.38 oz (266g)
Compared to 394 running shoes
tenis brooks ghost 13 azul vermelho preto
5.61 oz (159g)
Weight
12.59 oz (357g)

Breathability

The upper is a crucial component of every running shoe, and we found that Brooks has elevated the Glycerin series by offering not just one, but two different uppers. This is a great advantage, as it allows you to choose between the Glycerin 21 and the Glycerin StealthFit 21 based on your personal preferences.

If you're looking for a snugger, sock-like upper, the StealthFit is the best pick. However, our tests revealed a downside—ventilation is limited, with a rating of only 2/5. Thus, we can't recommend it for hot, summer runs.

In our light test, it quickly became clear that robust ventilation isn't a strength of this model. Barely any light passed through the upper, confirming our initial findings with the smoke-pumping machine.

zapatillas de running Brooks pie normal talla 43 blancas microscope

Brooks Adrenaline GTS 17 $120.

zapatillas de running Brooks pie normal talla 43 blancas micro 2

We discovered small ventilation holes in the toebox; however, an additional layer of knit beneath them hampers airflow. This setup isn't necessarily negative, as it makes the shoe ideal for colder weather.

Upon manually examining the upper, we were impressed by its elasticity, which allows it to conform closely to the feet for a sock-like fit. Yet, we noticed less padding in the heel—something to consider if you prefer substantial heel cushioning.

Test results
Glycerin StealthFit 21 2
Average 3.8
Compared to 323 running shoes
tenis brooks ghost 13 azul vermelho preto
1
Breathability
5

Durability

Toebox durability

The regular Glycerin scored 2/5 in our test, sparking our enthusiasm to evaluate the StealthFit variant to see if it could offer the much-needed enhancement.

Indeed, it does improve, albeit modestly, scoring 3/5. This outcome is encouraging, and from our perspective, it's sufficient to make us satisfied!

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Toebox durability
Test results
Glycerin StealthFit 21 3
Average 2.5
Compared to 257 running shoes
tenis brooks ghost 13 azul vermelho preto
1
Toebox durability
5

Brooks Defyance 11 Παπούτσια Για Τρέξιμο

With the Dremel in action, we also decided to test the heel durability of this SF variant, noting that it features significantly less padding.

Our assessment resulted in another 3/5 score—a bit disappointing, though it’s not a major concern.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Brooks Defyance 11 Παπούτσια Για Τρέξιμο
Test results
Glycerin StealthFit 21 3
Average 3.2
Compared to 253 running shoes
tenis brooks ghost 13 azul vermelho preto
1
Brooks Defyance 11 Παπούτσια Για Τρέξιμο
5

Outsole hardness

Shifting our focus to the outsole, we observed that it remains unchanged in the Glycerin 21. The outsole is constructed from the same durable Roadtack Rubber, which showed a hardness of 84.9 HC on our durometer test.

zapatillas de running Brooks pie normal talla 43 blancas outsole

This rubber effectively shields the high-wear zones on both the heel and forefoot. And despite a few areas of visible foam, these do not pose any issues in terms of wear and tear based on our experience.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Outsole hardness
Test results
Glycerin StealthFit 21 84.9 HC
Average 79.8 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 374 running shoes
tenis brooks ghost 13 azul vermelho preto
57.0 HC
Outsole hardness
93.0 HC

Outsole durability

Given the hardness of the rubber, we anticipated impressive results in our final Dremel test. Let's dive into the outcomes.

True to our expectations, even after rigorous application of the Dremel at 10K RPM, the rubber exhibited only a slight 0.5 mm indentation. This minor mark confirms the Roadtack's resilience.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Outsole durability
Test results
Glycerin StealthFit 21 0.5 mm
Average 1.0 mm
Compared to 235 running shoes
tenis brooks ghost 13 azul vermelho preto
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

In our concluding test of the outsole, we measured a thickness of 3.2 mm. This measurement is more than sufficient to withstand significant wear and tear, as indicated by our earlier test results.

zapatillas de running Brooks pie normal talla 43 blancas Outsole thickness
Test results
Glycerin StealthFit 21 3.2 mm
Average 3.2 mm
Compared to 391 running shoes
tenis brooks ghost 13 azul vermelho preto
1.0 mm
Outsole thickness
6.0 mm

Misc

Reflective elements

We feel that it's unfortunate Brooks opted not to include reflective elements in this StealthFit edition. This really feels like a missed opportunity to enhance safety and differentiate the product further. Maybe they'll consider it for v22?

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Reflective elements
Test results
Glycerin StealthFit 21 No

Tongue padding

One of the major weight reductions in the StealthFit 21 comes from the tongue. It transitions from a cushy 11.5 mm thickness to a minimalist 2.1 mm design.

zapatillas de running Brooks pie normal talla 43 blancas laces
The lacing system moves away from traditional eyelets to an integrated design with the sock-like tongue, making it impossible to tie a runners' knot.

For runners who favor thin, sock-like tongues, this one's a wonder—the benefits far outweigh any trade-offs. However, runners who prefer more padding in the instep might find this version a bit challenging.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Tongue padding
Test results
Glycerin StealthFit 21 2.1 mm
Average 5.8 mm
Compared to 391 running shoes
tenis brooks ghost 13 azul vermelho preto
0.5 mm
Tongue padding
14.2 mm

zapatillas de running Brooks mujer amortiguación media constitución fuerte 10k entre 60 y 100

One of our major letdowns with the Glycerin 21 was its non-gusseted tongue, which seemed lacking for a $160 shoe. Fortunately, the StealthFit version addresses this by introducing a superb sock-like tongue, providing an Alphafly-esque feel that many of us love.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 zapatillas de running Brooks mujer amortiguación media constitución fuerte 10k entre 60 y 100
Test results
Glycerin StealthFit 21 Sock like

Heel tab

Another lovely bonus with this variation is the inclusion of a convenient finger-loop heel tab—a truly handy feature.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Heel tab
Test results
Glycerin StealthFit 21 Finger loop

Removable insole

The insole easily comes out and can be swapped out as it's not glued to the last. It doesn't offer anything extraordinary compared to the GTS or the standard version.

zapatillas de running Brooks neutro ritmo bajo maratón talla 45 más de 100 21 Removable insole
Test results
Glycerin StealthFit 21 Yes