Recoil Reduction Device, 2 ports, Compensator, KeyMount In order to use this device with a suppressor, it must be installed by a professional - to ensure it is properly mounted and aligned. Do NOT shoot without checking alignment with bore rods. JMac Customs is not responsible for any damage to the suppressor, or any injury resulting from improper installation. Some firearms are NOT suitable suppressor hosts, just because you can thread this muzzle device on, does NOT mean it is safe to use. The RRD-2C is a shortened version of the RRD-4C by removing the 2 smallest ports creating a more compact package! At 2.23"" it still adds 1.53"" and can be permanent Mfg: Jmac Customs