Are you building a CETME L from a kit? Do you want spares to keep your MarColMar CETME L in top condition? This is a newly manufactured mainspring was developed from extensive high-speed video and photographic analysis of the CETME L action under fire. This spring is required to return the bolt and carrier into battery, and efficiently load the round and close the action for firing. The mainspring works in concert with our new made buffer spring, to keep your CETME L in good operating order.