BLACKHAWK! Adjustable AR-15 and M4 Buttstock, 5-Position, Mil-Spec Tube, Black: * Durable, reinforced polymer construction * Precision fit for quick and smooth length adjustment * Designed for comfortable cheek weld * Ambidextrous sling mounting locations with preinstalled 1" quick-detach sling swivel * Different models fit commercial and military carbine tubes * Measure rear tube diameter to determine fit: commercial 1.170"; military 1.146" * Limited lifetime warranty * K11000-C