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 tensil strength of over 10,000. The 520 chain has 120 links. We HIGHLY recommend the use of a master link press to press on the master link as the chains are designed not to have any slack.