components which are substantially similar to the outer wall 144 the pressure cap 150 and the bosses 156 to form the piston also a piston may alternatively be formed using any other suitable manufacturing process or combination of manufacturing processes and the piston may be constructed from a different material or combination of materials referring now to fig5 7 various views of the piston 112 are shown to depict its features in greater detail the piston 112 generally comprises a cylindrical tubular outer wall 144 having an outer surface 146 and an inner surface 148 one end of the outer wall 144 is sealed by a pressure cap 150 that is generally the leading portion of the piston 112 during a compression stroke of the piston 112 in the bore 133 in other words the pressure cap 150 leads movement of the piston 112 when the piston 112 moves away from the crankcase 134 of the compressor 100 a ring seat 152 formed as a recessed groove in the outer wall 144 is located near the junction between the outer wall 144 and the pressure cap 150 the ring seat 152 is configured to receive a ring seal not shown which.