Image is for illustration purposes only. Actual part may vary.

3949781CUM

SEAL

This is a Cummins quad ring seal, a square-profile O-ring used to create a leak-proof joint between engine components such as oil lines, filter housings, or injector tubes. Over time, seals harden and crack, causing oil or coolant leaks; they are replaced during routine maintenance or component repair to ensure proper sealing.