CMMG Mid-Length piston conversion replaces front sight base, handguard cap, handguards and bolt carrier on any gas operated AR-15 style upper. Piston systems operate cleaner due to hot gases being diverted at the gas block instead of the upper receiver. Piston is hard chrome plated and is removable from the front of the gas block. The one piece bolt carrier has an integral impingement key for maximum strength. Gas block has an on and off setting for use with a suppressor, or remove the piston and set the gas system to off for use with our .22 conversion system. For use on any AR-15 or M-16 with any any caliber and any barrel length with a Mid-Length gas system.