The adidas UltraBoost 21 'Crystal White Hazy Green' spotlights the running shoe's full-length Boost midsole with a metallic iridescent finish. The responsive cushioning technology is reinforced underfoot by adidas' Linear Energy Push torsion system and a Stretchweb Continental rubber outsole. Up top, breathable Primeknit construction in Crystal White features recycled Parley Ocean Plastic and zero virgin polyester. A molded heel counter in Hazy Green offers rearfoot stability.