The Fortis K2 Enhanced Castle Nut and End Plate System in FDE (Fortis Manufacturing part no. LE-BLK-K2-FDE) replaces the stock AR-15 castle nut and end plate with a design built to eliminate the classic backing-out problem. Fortis Manufacturing engineered two lockdown systems, K1 and K2, into its Lightweight Enhanced (LE) line, each built around a precision snug fit that seats and seals the castle nut onto the end plate without staking. There is no ratcheting mechanism and no set screws to back out or fail over time. At just 0.59 ounces (16.8 grams), it adds essentially no weight to a stock or brace build.

Key Specifications

• The LE lockdown system uses a precision snug fit that seats and seals the castle nut onto the end plate without staking.
• No staking is required to keep the castle nut in place, unlike a standard mil-spec setup.
• Eliminates ratcheting and set screws entirely, removing two common points of failure on a standard end plate.
• Weighs only 0.59 ounces (16.8 grams), adding negligible weight to a buffer tube assembly.
• Part of Fortis’s two-lockdown-system LE line (K1 and K2), an engineered alternative to a threaded set screw.

Frequently Asked Questions

Does this replace both the castle nut and end plate? Yes, the K2 system is a matched castle nut and end plate pair engineered to work together.

Will it work with a QD sling mount end plate? This listing is the standard K2 castle nut and end plate pair; check Fortis’s QD-specific end plate options if you need an integrated sling mount.

Buy the Fortis K2 Enhanced Castle Nut and End Plate System, FDE

Order it from our Lubbock, Texas gun shop and we will get it ready to ship as soon as it is available. Browse more AR buffer system parts to finish your build.