A retaining ring is a fastener that holds components or assemblies onto a shaft or in a housing/bore when installed in a groove. Once installed, the exposed portion acts as a shoulder which retains the specific component or assembly.

Self-locking retaining rings may be installed in applications where no groove exists.

Retaining rings are typically made from carbon steel, stainless steel

Stainless steel

In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

 or beryllium copper

Beryllium copper

Beryllium copper , also known as copper beryllium, beryllium bronze and spring copper, is a copper alloy with 0.5—3% beryllium and sometimes with other alloying elements. Beryllium copper combines high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming...

 and may feature a variety of finishes for corrosion protection depending on the type of environment in which they are used.
There are three main types of retaining rings available, each of which may then be broken down into sub-types depending on unique application needs:

• Tapered section
  • Axially assembled
    • Inverted
    • Beveled
    • Bowed
  • Radially assembled
  • Self-locking
• Constant section
• Spiral

Tapered section retaining rings decrease symmetrically from the center to the free ends, remaining circular when contracted or expanded within the limits of normal use.