Abstract: A walking beam compressor has a rod collar assembly attached to the top cap of the compressor cylinder with bearings which reduce side loading on the seals and bearing surfaces in the top cap. A top cap assembly supports a pair of vertically stacked seals sandwiched between three inserts. Upper and lower inserts each house a wear ring so that the respective wear rings are above and below the seals. The piston is divided into an upper section and a lower section to facilitate the mounting of a peripheral seal at the mating surfaces of these sections. The peripheral edge of each section has a recess for receiving a wear ring. A structure is provided to facilitate separating the upper and lower sections during disassembly.