You get precision-machined steel construction that resists wear and extends chain life. JT rear sprockets are made from Japanese 545C high carbon steel and shaped with computer-controlled cutting equipment for exact tooth profiles and smooth power transfer. Features Japanese 545C high carbon steel outlasts mild steel and surface-hardened sprockets by two to three times Computer-designed and CNC-machined tooth profiles deliver precise chain engagement and reduced friction Heat-treated construction hardens the material for maximum durability under load Hand-finished surface meets or exceeds original equipment standards for fit and performance Induction hardening and black zinc finish available on select models for additional corrosion resistance