The adidas UltraBoost 21 "Triple Black" delivers a stealthy iteration of a performance running shoe that takes advantage of more Boost cushioning and a more responsive ride than its predecessor. A flexible Primeknit upper, incorporating Parley Ocean Plastic and other recycled materials, sits atop a black Boost midsole that packs 6% more Boost capsules. Underfoot, Linear Energy Push technology provides 15% more forefoot stiffness to produce improved energy return with each step.