E-Type retaining rings, also known as side-mount external retaining rings or just e-clips, are a retaining ring with three prongs that lock into grooves on shafts. Their unique shape allows them to provide greater retaining surface area than standard retaining rings allowing them to have greater holding power. They are made to seat into machined grooves on shafts. axles, gears, and bearings, maintaining constant pressure on the housings to prevent slippage. Tools are required to install and remove them. Made from spring steel for strength and are either black phosphate coated or zinc plated for moderate corrosion resistance.