Original Item: From our recent importation of Bren parts, these are complete bolt carriers with attached gas pistons, or operating rods. This item helps to capture the energy from the gas-recoil system, and cycles the bolt.
This is the MkI version of the Bolt Carrier and Gas piston, which has more complex machining on the Gas piston, similar to the Czech ZB 26 and 30, which the Bren was based on. Bren is a combination of BRNO, the Czech arms factory that designed the ZB30/26, and Enfield, the location of RSAF Enfied.