Prosole Insoles made by Sorbothane are shock absorbing insoles that provide extra cushioning & shock absorption across the full surface of the insole. Simply fit them on top of existing insoles to reduce stress during impact, for the prevention & relief of running related injuries. How do they work? Sortbothane is a unique synthetic material that mimics the characteristics of human tissue. Its molecular structure allows it to recover its shape completely after each 'shock' &, used as a heel pad in footwear, it absorbs 94.7% of the shock waves caused by the heel striking a hard surface. This means it reduces muscle fatigue, helps protect weak joints & eases the strain on ligaments & tendons. When can I use them? For the prevention & relief of Achilles Tendonitis & Calf muscle strains during distance football (soccer), Football & golf. Sorbothane Sports Prosoles are ideal for the prevention & relief of Achilles Tendonitis (Achilles Tendinopathy), Achilles Paratendinopathy, Calf muscle strains & heel pain in people who run or participate in other sports. Simply place them over the insoles in your existing sports footwear & reduce the shock on your body. Specially designed for studded footwear, ideal for the rigors of the game Which size do I need? Sorbothane's sizing is based on UK mens shoe size.