My RIX SA3 compressor has a 3rd stage piston that FLOATS in the cylinder, unattached to the piston rod. Pressure is what keeps it in contact with the piston rod. The RIX manual says one of the functions of my Back Pressure Regulator is to get the pressure up fast so that this piston gets into contact with the piston rod and stays that way. So, its not really a cushion as much as it is part of the piston/piston rod connection method.