O-Rings are round rubber washers that are placed around the valve stem in order to create a seal, preventing leaking from occurring and providing an excellent resistance to vibration. The listed size is referenced from AS568 dimensions, which is the Aerospace Size Standard for O-rings from the Society of Automotive Engineers.
Silicon Specs:
- ASTM D 1418 Designations: , VMQ, PVMQ
 - ASTM D 2000, SAE J200 Type/, FE, GE
 - General Temperature Range: -65 to +450 Degrees (F)
 
Silicon Performs Well In:
- Engine & transmission oils (mineral oils)
 - Ozone
 - Dry heat
 
Silicone Does Not Perform Well In:
- Petroleum oils & fuels
 - Ketones (MEK, acetone)
 - Steam
 - Concentrated acids