Leapers RB-A005 UTG Model 4/AR15 Receiver Wedge. Accuracy Wedge Fits Model M4, AR15, M16 rifles and Instantly tightens loose upper and lower receivers. Accuracy wedge fits into the rear of the lower receiver and keeps the upper section snug and tight Increases accuracy, decreases vibration and prevents wear. Fits any AR15, M16 and M4 rifle, carbine or pistol. QTY (1).