The FAB Defense GLR-16 Buttstock for your AR15/M16 provides you with enhanced versatility with it's stock extension and optional adjustable Cheek Rest. FeaturesUniquely designed rubber butt pad for fast and stable shoulder positioningUnique patented Anti-Rattle mechanismfits perfectly on Mil-Spec and commercial after-market buffer tubesThree Integrated Slots for Sling AttachmentOne in the Front and Two at the RearTwo Ambidextrous Metal Quick Release Rear Sling Mount PointsWater-resistant anti rattle storage compartment for two CR123 or AA batteriesMaintains Contour & Size of Original DesignMade from fiberglass reinforced polymer composite.