Specific design of sealed-in lubrication maintenance for bearing system in each link makes the complete chain work to its optimum wear life. For KMC O-Ring chain, superior alloy steel is adopted and heat-treated to provide best performance in strength. In addition, special formulated grease contained by O-Ring in the interface between solid bushing and hardened pin keeps giving constant interior lubrication, and extremely enhances the efficiency and effects on friction elimination during operation. Least wear results in least stretch in chain, and let prolong its service life 5-10 times than standard chain