DID 520 ERVT - Drive Chain - 120 Links977023688 Product Description 520ERVT breaks down the concept of the original motocross chain (non o ring) and adds the benefits of an x ring X Ring helps keep your chain sealed with lubrication, limits dirt and mud from getting in between the side plates, and only has 4 contact points with the plates which means less friction than the traditional O Ring chain More lightweight and longer chain life By adjusting the materials, the 520ERVT is now 2%