This threaded roll pin is designed to work with Aero Precision’s M4E1 Lower Receiver. It will not work with their M5 Lower Receiver or AR-15 Gen 2 Lower Receivers.

NOTE: This product is already included with the Aero Precision M4E1 Lower Receiver. It is not necessary to be purchased separately. This individual product is available for customers who have lost or damaged their existing M4E1 threaded bolt catch roll pin.