What are Oil Seals? 6 Things DIYers Should Know

3) Seal numbering system

ERIKS type GV (type C according to DIN) is equivalent to type M, but is a heavy-duty version with a double metal casing. This can be a useful solution with larger diameters in more demanding applications. There is also a version of this type with a dust lip; the GVST (type CS according to DIN).

To ensure correct fit and proper protection against contaminants, the inside diameter of an oil seal must be slightly smaller than the shaft diameter. 

Unthinkable in the list of seals are oil seals, which provide a seal against splashing oil. The most important oil seals are used for rotating shafts and valve stem seals. Oil seals are intentionally never completely sealed to lubricate the seals and prevent wear.