The Strike Industries Modular Fixed Stock combines the versatility and adjustability of a collapsible stock with the strength ergonomics and solid fit of a fixed stock. The SI MFS uses a standard carbine length receiver extension and is adjusted using the included shim set to change length of pull.Features customizable Length of Pull 12″ to 14.25″ modular assembly Snap Hook attachment and sling loop and for mil-spec carbine or our Advanced Receiver Extension 7-Position buffer tubes only.