The GLR-16 Buttstock for your AR15/M16 provides you with enhanced versatility with it’s stock extension and optional adjustable cheek rest. It features uniquely designed rubber butt, Anti-Rattle mechanism which fits perfectly on MIL-SPEC and commercial after-market buffer tubes, and is made from fiberglass reinforced polymer composite. The stock also has a water-resistant anti rattle storage compartment for two CR123 or AA batteries.