The oil seal (in NBR or FPM) is a seal for a rotating shaft where the medium to be sealed is not under pressure. In stationary condition, sealing takes place through the preload of the sealing lip, aided by the spring behind this lip. In the dynamic condition, the specially designed shape of the sealing lip works through "aqua-dynamic" principles, which means that a film of the fluid to be sealed works its way between the sealing lip and shaft, causing the actual sealing to take place. This has the advantage that through the liquid there is as little friction as possible, allowing high shaft speeds.

Note: Any suffixes 'ZV' and 'OF' indicate a type without spring.