POC's Bone VPD Arm pads are serious armor that laugh off hits from rocks, the ground, whatever. The outer shell is cut from sturdy, ventilated PolyPro mated to an inner Visco-Elastic Polymer Dough layer. The dough forms to your arms and is flexible when moving, then turns rigid upon impact. Straps lock them in place so they don't shift while riding and more importantly, crashing. The Bones are articulated in three segments providing extraordinary fit, comfort and protection too.