What Our Gearhead(R) Experts Are Saying:"I wore the Glycerin GTS 23 through a full block of marathon training and the plush cushioning held up beautifully on back-to-back long run weekends without ever feeling worn down. The GuideRails support is subtle when your form is good and present when it starts to slip, which is exactly the kind of smart shoe technology that makes a real difference over twenty-plus miles."The Brooks Glycerin GTS 23 is designed for the runner who takes their long runs seriously and wants a shoe that matches that commitment. From the first easy mile to the final hard one, it delivers a level of cushioning and support that holds steady when legs start to tire and form starts to falter. The plush midsole absorbs the relentless impact of road miles with a softness that feels almost indulgent, and the accommodating fit gives the foot the room it needs to settle in naturally for the duration of a long effort. What makes the Glycerin GTS 23 more than just a comfortable shoe is the GuideRails Technology System working quietly beneath the surface. Rather than forcing the foot into a fixed motion path, GuideRails monitors excess movement at the heel and knee and intervenes only when needed, providing structured support that feels earned rather than imposed. Plush, tuned cushioning powers the toe-off with surprising energy for a shoe this soft, keeping the ride from feeling sluggish even when the mileage climbs. With over 60% recycled materials in the upper, the Glycerin GTS 23 brings the same thoughtfulness to its construction that it brings to every mile underfoot.