Surly singleator spring loaded chain tensioner for running single speed on non adjustable chain tension framesfit to rear mech hanger positionsurly singulator features cnc alloy body variable chainline floating tension pulley stainless steel pivot bushing triple sealed reversible springcompatible with 18 and 332 chains11t jockey and slotted alloy chain rejection side platesall in all the mutts nutts of ss chain tensioners