This is a A-50X31 Sprocket PN: 50X31Main Description As Following : A-50X31 Sprocket P.N: 50X31 Hub Required: XInside Diameter: 2"Outside Diameter: 6.521"Teeth: 31 Crossed From: WSS105031 , , 20005031 , , 20005031 , , 3016-0202 , Found in Section & Models : Chains/ Sprockets/ Pulleys/ Hubs > Sprockets, (Miscellaneous) (UNDEFINED): SEVERAL Associated Items : New Also This is An Aftermarket Product And : Hub Required: X Inside Diameter: 2" Outside Diameter: 6.521" Teeth: 31