Internal retaining rings feature a spring steel ring with "ears" on both ends with the holes facing to the center of the ring, which is why they are termed internal. They are made to seat into machined grooves on shafts, axles, gears, and bearings, mainting constant pressure on the housings to prevent slippage. Pliers are required to install and remove these retaining rings. Made from spring steel for strength and zinc plated for moderate corrosion resistance.