Glycerin 20 vs. Glycerin 21: The next step in cushioned running shoes

The Glycerin story: More cushion. More softness. Less gravity.

As one of our most popular cushioned running shoes, Glycerin has always prioritized comfort, protection, and support—and sometimes broken new ground on the way. Back in 2018, for example, Glycerin 16 became the first shoe to feature our exclusive DNA LOFT technology for a lightweight-yet-luxurious ride.

Having been regarded by some as a recovery trainer in the early days, Glycerin is now firmly established as a high-performing daily running shoe for both long runs and speedwork. Each Glycerin launch carries that legacy forward while offering new innovations, thoughtful touches, and an even more refined balance of speed and comfort. But which Glycerin will fit your run best?

Glycerin 20 vs. Glycerin 21: A side-by-side comparison 

Glycerin 20 and Glycerin 21 have a shared heritage, but there are some subtle points of differentiation between the two. Here’s how they compare in five key areas:

1. Plush cushioning: Although both shoes feature our latest nitrogen-infused DNA LOFT v3 cushioning, Glycerin 21 has an additional 2mm of it underfoot. That makes it our most cushioned running shoe yet.
2. Improved upper: Glycerin 20’s breathable air-mesh upper offers a secure and comfortable fit. Glycerin 21’s new engineered warp knit upper is also breathable but provides structure in crucial locations across the foot.
3. Custom fit: Both the Glycerin 20 and Glycerin 21 offer a choice of classic fit or StealthFit, which molds closely to your foot. Both shoes are also available with go-to-support (GTS) via our GuideRails® technology.
4. Sole technology: Glycerin 21 is the first shoe in the Glycerin series with our new RoadTack rubber, a resilient, lightweight compound made using a mix of rubber and recycled silica.
5. Smooth transitions: Glycerin 20 and Glycerin 21 feature a redesigned midsole and outsole, creating a widened platform for greater stability and smoother heel-to-toe transitions.

Glycerin 20: Supremely soft yet speedy

Although it’s designed primarily for luxurious comfort, Glycerin 20 doesn’t rest on its laurels. This cushioned running shoe is packed with comfort-first innovations like a widened platform and an all-new engineered mesh upper, allowing runners to forget their feet and let their minds run free.

Alongside Caldera and Hyperion, Glycerin 20 was one of the first Brooks Running shoes to feature nitrogen-infused DNA LOFT v3 foam, our softest cushioning. Molecular biologist Dr. Raven Baxter explains the science behind the softness:

If you want personalized advice on how much cushioning you need, visit your local running store or try our shoe finder for a self-assessment.

Glycerin 21: Float through your run

Featuring more of our DNA LOFT v3 foam than any other running shoe, Glycerin 21 keeps your feet feeling firmly off the ground. What’s even better is that all that comfort doesn’t come at the cost of performance—this is a balanced, lightweight blend of responsiveness and support for mile after mile of distraction-free running.

Glycerin 21 is also available in custom configurations for the right fit. Glycerin GTS 21 uses GuideRails® support to keep you moving comfortably while supporting the most injury-prone part of a runner’s body: the knees. Both the Glycerin 21 and Glycerin GTS 21 are available in StealthFit, now featuring an updated FitKnit upper that molds to your foot for a blend of stretch and compression. This new configuration is designed to move with you, while the new materials feel super soft against your foot.

Hello Glycerin, goodbye gravity