The Magpul® UBR™ (Utility / Battle Rifle), U.S. Patent 6651371, is a fully-featured, adjustable butt stock for the AR15 / M16. Unlike typical collapsing stocks, this modular design offers the stability of a fixed stock with consistent cheek weld in any position. Seven-position length-of-pull (LOP) adjustment is quickly executed with gross motor movement while the integral preset system allows direct access to a preferred position. A robust lock mechanism and multi-shell construction increase durability under severe impact conditions experienced during malfunction clearing and accommodates large-bore AR calibers. The UBR™ also provides extra counterbalance weight to improve handling on full-length rifles and weapons with muzzle-heavy accessories or grenade launchers. Optional components such as dual-side sling mounts and metal strike plate allow the UBR™ to adapt to the mission at hand.