RK Racing Chain 428SO-126 Steel 126-Links Heavy Duty Chain with Connecting Link The 428SO is one of the best O-ring chains in the industry 428SO chains feature heat treated hi-carbon alloy steel components with seamless rollers and shouldered bushings for strength and durability, and are fitted with O-ring seals O-ring seals are made from an advanced Nitrile butadiene composite for maximum performance and wear life Nitrile butadiene O-rings seal in lubrication and deliver smooth power with no O-ring drag or loss of horsepower The 428SO has a tensile strength rating of 4420 foot pounds and is rated for bikes up to 125cc