ASICS Men's Gel-Challenger 11 Tennis Shoe 100% Synthetic Imported Rubber sole Flexion Fit Upper: Proprietary upper which provides form fitting comfort without sacrificing support. PGuard Toe Protector: Enhanced toe durability. Rearfoot and Forefoot GEL Cushioning Systems: Attenuates shock during impact and toe-off phases, and allows movement in multiple planes as the foot transitions through the gait cycle. P.H.F (Personal Heel Fit)Collar Lining: 2 layers of memory foam line the collar and mold to the athlete's heel, creating a personalized fit. Solyte Midsole Material: A lighter weight midsole compound than ASICS' standard EVA and SpEVA. Also features enhanced cushioning and durability.