The GLR-16 Buttstock for your AR15/M16 provides you with enhanced versatility with it's stock extension and optional adjustable Cheek Rest. - Advantages: - Uniquely designed rubber butt pad for fast and stable shoulder positioning - Unique Integral Pressure System Applies Constant Pressure on the Buffer Tube by Closing Gaps Around the Buffer Tube Eliminating Rattling and Noise - Three Integrated Slots for Sling Attachment One in the Front and Two at the Rear - Two Ambidextrous Metal Quick Release Rear Sling Mount Points - Water proof anti rattle storage compartment for two CR123 or AA batteries - Fits Perfectly After Market Tube with a Perfect Non Rattling Fit - Maintains Contour & Size of Original Design - Made from fiberglass reinforced polymer composite - Available in the GPCP Version with an Adjustable Cheek Rest & Dual Picatinny Raills or in the Standard GCP Version with an Adjustable Cheek Rest.