Spenco Walker Runner Insole For walking, running and jogging. Special 'heel strike' cushioning delivers optimum shock absorption for repetitive rear foot impact. 4-Way Stretch Fabric with Ultra-Fresh Silpure Antimicrobial helps prevent blisters while controlling odor. Air Injected Spenco Material. A 5/32-inch layer of this material absorbs shock and impact to provide intense comfort and cushioning. Molded Polyurethane.