Kingfoam 5mm Flat Skeleton Insole. Low Profile. All FP products are made with a special formulation of ARTi-LAGE (Artificial Cartilage Foam) which is the world’s most impact absorbing material. In fact, our Insole Skeleton absorb 2-3 times more impact than any other Insole Skeleton out there. ARTi-LAGE works by converting impact energy into heat before the energy can reach your body.