Retaining rings are used to help secure sockets onto drive tools. They are not intended to bear any load. The rotational forces are between the drive tool and the socket. The resin crush gauge on the pin helps indicate when a socket is excessively worn and should be replaced. Drive tool and socket should line up when in use and should not pinch the crush gauge. Cracked sockets and/or worn drive tools cause each other to turn excessively in relation to each other. This action pinches the small fin or the crush gauge on these retaining rings. If the crush gauge is pinched, it is an indication that the socket and or the drive tool need to be replaced. One-piece construction, no loose parts. Pin is made of resin which allows the material to compress without breaking. Part numbers are embossed on the rings near the point at which the pin and ring meet.