Upgrade your CPS TRS21 with RK MAC's easy service 2 piece SS piston design.  This kit comes with a fully assembled connection rod with the 2 piece piston.  You will also get RK MAC's exclusive long life GEN III piston seals and wear bands along with other improvements over the original OEMs design. GEN III seals last 700% longer than the OEM seals.  This kit utilizes a Viton energizing O-ring for Butane or Propane recovery used in the Oil Extraction Process.
 
Compressor Rebuild Manual