The Brooks Glycerin GTS 21 Running Shoes combine super-soft cushioning and supreme comfort. These shoes are equipped with a new, engineered warp knit upper that is breathable and allows for a flexible, accommodating fit while staying soft against your foot. Their GuideRails holistic support system offers Brooks™ innovative technology that supports your body in its natural motion path while keeping excess motion in check. Their new RoadTack rubber includes recycled silica and is both lightweight and durable. They feature an additional 2 mm of DNA LOFT v3 midsole for a plush ride. Each pair are made with recycled materials equivalent to 5 plastic water bottles.