SEAL，O RING

An O-ring is a round rubber sealing ring that sits in a groove to seal a joint against fluid or gas.

Compressed between two surfaces, it deforms to fill the gap and blocks leaks even under pressure; the material is matched to the fluid and temperature.

O-rings seal connections in the fuel, hydraulic, cooling, and air systems. The correct O-ring matches the groove size and the fluid it must resist.