Disperses heat and runs cooler than other close-to-the-barrel rail systems. Comes with built-in, spring-loaded BattleSight for added versatility. Low-profile locking mechanism delivers unparalleled strength and stability. Machined from 6061-T6 hardened aircraft aluminum and finished in mil-spec type-III hard-coat anodizing. Comes with three detachable rails and all mounting hardware. Works with standard AR-15/M-16 barrel nut. Made in USA. Available: 11", 13".