Upgrade your AR-15 / AR-9 with the Fortis Manufacturing K1 Tapered System, the ultimate lightweight castle nut and enhanced endplate combo that delivers uncompromising performance without adding unnecessary weight. Weighing in at just 16.8 grams, this innovative combination offers a significant reduction in weight compared to a milspec lock nut and endplate, without sacrificing durability or reliability. But the Fortis Manufacturing Tapered K1 System is not just about weight reduction - it also offers enhanced features including a built-in QD sling swivel attachment point and a tapered castle nut that seals itself onto the end plate. This virtually eliminates the possibility of your castle nut backing off without the need to stake! No ratcheting, no set screws, no backing out and no failures. Manufacturer part number: LE-BLK-K1-BLK K1 System Specifications: Lightweight design at only .59 oz / 16.8 grams total Castle nut and end plate are 7075 T6 Aircraft Grade Aluminum Quick Detach Socket - 360 degree rotational locking interface No set screws or ratcheting system Made in the USA