The FSM is the standard Folding Stock Mechanism. It fits between the Receiver Block and Modular Stock. The FSM can be mounted to fold either left or right. Will add .75” to your LOP and weighs 3.5 oz.The FSM is manufactured with and without the Boss. The Boss is the raised (oblong shaped) portion on the Arm (small side). If you require one with or without the Boss pleases specify in the Order Instructions section during the checkout process. If you do not specify your order will be shipped based on availability.
Push Button actuated folding mechanism can be made to fold left or right by inverting the mechanism on the receiver block
If you are ordering a receiver block with your folding stock mechanism we recommend you use an FSM with a boss.