A compressor having a cylinder bores and pistons are disclosed. Each piston moves in the associated cylinder to compress gas therein. Each piston slides on an inner peripheral wall of an associated cylinder to seal a compression chamber. Each piston includes an outer peripheral surface and cavities. The outer peripheral surface has a seal to seal the cylinder and a pressure receiving surface to receive reaction forces from the wall of the cylinder. A low friction layer is formed on the pressure receiving surface. The layer facilitates the sliding movement of the piston with respect to the cylinder.
