Out-gassing
If you find a gap, measure it by sliding a feeler gauge under the ruler.
After the oil seal is positioned in the groove, apply even pressure to the oil seal using a seal driver or a similar tool. This will help to seat the oil seal firmly in the groove and prevent it from moving during use. Make sure to apply the pressure evenly and gently, as applying too much force can damage the oil seal or cause it to deform.
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What are Oil Seals and how should they be ordered?
Polyurethane
2) Special seal types and their features
The quality of the rubber or rubber fabric used to make an outer case is the same as the quality of the rubber sealing lip. Fabric reinforced rubber is, as the name suggests, rubber reinforced with a fabric.