AR 15 Windham Weaponry Buffer Retainer Kit: Made in USA 1x Buffer Retainer The Buffer Retainer (along with its spring) holds the Buffer & Action Spring within Rec. Extension Tube in Lower Receiver. Machined steel with black phosphate finish. 1x Buffer Retainer Spring for AR15 A high tensile strength coil spring – fits into Buffer Retainer in Lower Receiver to hold Buffer & Spring within Rec. Extension Tube.