PolySorb® Heavy Duty Replacement Insoles are proven to deliver the best combination of shock absorption and energy return. They help reduce friction while improving overall foot comfort. A contoured layer of lightweight polyurethane is bonded to nitrogen-injected closed-cell Spenco® material to provide oustanding cushioning and foot stability. These insoles return energy with special heel strike cushioning for people who are on their feet all day. Durable and washable.