Racing Boss The 520ERVT is designed as our top-of-the-line enduro chain, but it's strength, lightweight, and extended chain life makes it an ultimate racing chain. X-Ring Technology Born from our original non-o-ring motocross chain, the ERVT boasts our patented X-Ring technology which provides less stretch, a higher tensile strength, and ultimately a longer lasting chain. Strong, Yet Light This is our lightest and longest lasting X-Ring chain in the 520 size.