Doublestar-ACE's Standard Folding Stock Mechanism (FSM) with Boss fits between the rifle's Receiver Block and the Modular Stock (not included). The FSM can be mounted to fold to either the left or right. It will add .75" to your Length of Pull and weighs 3.5 oz. The Boss is the raised (oblong shaped) portion on the Arm (small side).

Features:
Standard folding mechanism with BOSS
Can be mounted to fold either left or right