This A2 style fixed stock kit fits standard Mil-Spec AR-15 lower receivers. The kit includes a rifle length receiver extension tube, A2 buffer, buffer spring, spacer, and screw. The hinged butt plate provides access to the internal storage compartment. Made of durable, impact resistant polymer.This A2 style fixed stock kit fits standard Mil-Spec AR-15 lower receivers. The kit includes a rifle length receiver extension tube, A2 buffer, buffer spring, spacer, and screw. The hinged butt plate provides access to the internal storage compartment. Made of durable, impact resistant polymer.