EK invented the O-ring chain for motorcycles way back in 1974, and while other manufacturers have adopted O-ring construction for their chains EK has improved the concept with the Quadra-X Ring seal. It reduces friction by as much as 40 percent and offers even better grease sealing qualities than a conventional O-ring because it has twice as many contact points between the ring and sideplates.
The Quadra-X Ring technology is available throughout the range of EK chains that cover everything from a stock replacement or something even stronger to handle big horsepower applications like turbo bikes. Optional colors and Zero Stretch Technology are also available for some applications, so check out the Web site for your specific application.
$ varies per application
ekchain.com