The 520SO is one of the best Oring chains in the industry 520SO chains feature heat treated hicarbon alloy steel components with seamless rollers and shouldered bushings for strength and durability and are fitted with Oring seals Oring seals are made from an advanced Nitrile Butadiene composite for maximum performance and wear life Nitrile Butadiene Orings seal in lubrication and deliver smooth power with no Oring drag or loss of horsepower The 520SO has a tensile strength rating of 7700 foot pounds and is rated for bikes up to 400cc