CHAIN

Provided is a seal ring which can be easily mounted into a chain, can be maintained stably in the mounted state, and can exhibit consistent sealing performance. A seal ring for sealing a chain is mounted in an axially compressed state between an outer link plate which is disposed on the outer peripheral side of a connection pin and an inner link plate which is disposed on the outer peripheral side of the connection pin with a bush provided therebetween. The seal ring has an annular base section, a first outer peripheral lip, a second outer peripheral lip, a first end surface lip, a second end surface lip, and an inner peripheral protrusion. When a bush is press-fitted to the inner peripheral side of the seal ring, the inner peripheral protrusion comes into contact with the bush to generate rotational moment which obliquely twists the seal ring. When the twisting occurs, the first outer peripheral lip and the second outer peripheral lip come into contact with the outer link plate or the inner link plate while falling radially outward.