Retaining rings are metal fasteners that fit into a groove on a shaft or in a housing or bore to provide a shoulder that holds an assembly in place. The purpose of a Retaining Ring is to act as a shoulder to stop the sub-component or assemblies coming off the shaft or housing bore, especially in mechanical power transmission assemblies. Various manufacturers offer various retainer rings, but all of them can be grouped under stamped and spiral wound rings. 

As the name suggests, Stamped ring, sometimes called snap rings, gets the name as it’s stamped from tempered sheet metal and has a non-uniform cross-section.  Various designs are available from various manufacturers catering and addressing common shortfalls of the rings such as tolerance stack-up, clearance diameter, thrust load capacity, flexible and radial installation, and assembly automation.

The most common types of rings are;
External and internal circlips
E-clips
Spiral Rings
External and internal Snap Rings