Presma Aluminum Castle Nut for .223/5.56/.308 Buffer Tube Receiver End Plates Black. This durable receiver end plate/buffer tube castle nut is machined from 7075 T6 aluminum for a strong lightweight platform. The machined receiver end plate/castle nut helps prevent any unwanted nipples from forming and is a crucial part of overall receiver installation. This receiver end plate/buffer tube castle nut should be installed at each end of the buffer tube instead of each individual end of the buffer tube. Please refer to your manual for proper bolt removal/adjustment. Specifications for Presma AR Buffer Tube Receiver End Plate Castle Nut: Manufacturer: Presma Condition: New Fabric/Material: 7075-T6 Aluminum Quantity: 1 Features of Presma AR Buffer Tube Receiver End Plate Castle Nut High Quality 7075-T6 Aluminum Construction Package Contents: Presma AR Buffer Tube Receiver End Plate Castle Nut Presma ABNT03: Aluminum Castle Nut for .223/5.56/.308 Buffer Tube Receiver End Plates Black