If your air compressor runs but does not pump air after a couple years of service, chances are the diaphragm has cracked. These kits include the diaphragm, head gasket and other parts needed to rebuild compressor to 'like new' performance. DC12RK is also used on our old 1/3 HP diaphragm compressors (DC13) as well as the DC12 (1/8 HP).