Several years of development and thousands of hours of testing have fine-tuned the latest S&S Cycle Cam Chain Tensioner for the M8 platform.  Larger piston diameter, tighter tolerances, thicker shoe material, and built-in direct chain oilers make the new S&S hydraulic chain tensioners the best option for 2017 and later Harley-Davidson® M8 owners running chain drive cams. Direct replacement for factory #25500013. Made in America, these billet tensioners will add longevity and performance to your valve train and are a must have for cam upgrades. Check out the new Hydraulic Cam Chain Tensioner for M8 models on their site or hit up your local dealer for more info.   https://www.sscycle.com/products/cam-chain-tensioner-for-2017-up-m8-models/