The KynSHOT RB5007 Recoil Buffer is a hydraulic buffer system designed and optimized to fit 9mm PCC’s using a Mil-Spec style carbine buffer tube (internal depth 7″). The RB5007 can be paired with any style buffer spring, and is a simple drop-in replacement for all buffer systems on the market. The RB5007 can be used with an A5/AR-10 buffer tube (internal depth 7.75″). If you are shooting a CMMG Radial Delayed Blowback system, the buffer does not need to be paired with a spacer weight.