Rotary shaft seals, also known as radial shaft seals or more commonly called oil and grease seals, help prevent lubricant leakage by retaining the fluid within the application while simultaneously protecting it from the intrusion of dirt, dust and other harmful external contaminants. Shaft seals consist of a metal body, an elastomeric sealing lip and a garter spring. Based on these characteristics, rotary shaft seals can be divided into different categories: shaft seals with rubber coated or metal cased OD, shaft seals with a single primary sealing lip or with a primary lip combined with an additional secondary dust lip, shaft seals energized by a steel/stainless steel spring (spring-loaded) or with a non-spring-loaded sealing lip. Rotary shaft seals are readily available from stock in both Metric and Imperial (inch) sizes in the most commonly used elastomeric materials: Nitrile rubber (NBR), Fluorocarbon rubber (FKM/FPM) and Silicone rubber (VMQ).