The bloody little part doesn't belong to the rifle,belongs to a watch press that I haven't used in years and fell out ofthe box onto the rug under my desk. When taking the AR apart stuff went flying thru the air onto the rug and of course I collected all the parts I could find .....Funny thing the little bugger fit the buffer retainer hole in the rifle. So thanks,sure got a good education on the AR. I apologize...Spad