Mika Metals X Ring Factory Series Chains use exclusive next level bushings that slow elongation of the chain and increase chain life. The X ring design of the seals reduces friction by over 50% compare to standard O ring chains. It is one of the lightest and strongest off road (X ring or O ring) chains on the market with a tensile strength of over 10,000. The 520 chain has 120 links. The use of a master link tool press to install the chain is REQUIRED as our chains are designed not to have any play in them.