Gear Head Works Castle Nut and End Plate Set Black. You will need a Tailhook Mod 1 and buffer tube to complete this package for your AR. This kit comes unassembled. Specifications for Gear Head Works Castle Nut and End Plate Set: Manufacturer: Gear Head Works Color: Black Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Package Contents: Gear Head Works Castle Nut and End Plate Set What firearm models does the manufacturer say Gear Head Works Castle Nut and End Plate Set is compatible with? The manufacturer says that Gear Head Works Castle Nut and End Plate Set is compatible with AR-15Gear Head Works GHW-36: Castle Nut and End Plate Set Black