The Brooks Glycerin 20 is one of the few models that allow you to customize the style and level of support in your shoe. Customers can choose between the regular fit or the stealthfit, which is more streamlined and snug. From there, you can choose between a neutral level of support or a more supportive style. All combinations are engineered with a nitrogen-infused DNA V3, a cushioning technology designed to provide maximum cushion and responsiveness while keeping the shoe lightweight.
Another upgrade with the Brooks Glycerin 20 is a redesigned midsole and outsole which is intended to create a smooth heel-to-toe transition. The new design is wider, and the rubber on the outsole has a larger surface area than previous models. However, several reviewers found this model to feel bulky and the extra rubber to actually inhibit a smooth heel-to-toe transition.
If you plan on running in dim light, be aware that there is no reflective detailing on the upper mesh (which is very breathable).