Primary Weapons Systems Ratchet Lock End Plate & Castle Nut Set Black AR-15. These AR15 Lower Parts from Primary Weapons Systems are made of 4140 steel and can be removed easily if needed. The Primary Weapons Systems End Plate & Castle Nut Set is compatible with both commercial and Mil-Spec sized buffer tubes. Choose the Primary Weapons Systems Castle Nut & End Plate Set for easy installation and a solid feel. Specifications for Primary Weapons Systems EBT Mod 2 End Plate and Castle Nut: Manufacturer: Primary Weapons Systems Color: Black Fabric/Material: 4140 Steel Gun Make: AR Platform Condition: New Features of Primary Weapons Systems Ratchet Lock Castle Nut & End Plate Set for Buffer Tube Installation: Ratchet-lock design eliminates need for staking the castle nut. Compatible with Mil-Spec and Commercial buffer tubes. Integrated QD mount. Made of 4140 steel. Rock solid lock up. Easy installation and easy removal if needed. Package Contents: Primary Weapons Systems EBT Mod 2 Ratchet Lock Castle Nut End Plate Set 4BTRLPB1 Ratchet Lock Castle Nut Endplate Set