ACTION CHAIN TENSION ADJUSTER MKS TRACK 8MM Review Posted by GiantPandaisy June 4, 2018 in Drivetrain Components MKS Track chain tensioner. Keep proper chain tension like a Keirin racer with this NJS approved steel chain tensioner. Allen head adjustment bolt, for 8mm dropout thickness on aluminum frames, 10mm axle diameter, steel. CA-MX10 Action Cycling Outdoor Recreation Parts & Components Sports & Outdoors