For tapered 50mm/57mm OD head tube For 1.5` headtube and 1-1/8` steerer 1-1/8 alloy internal cup with 36?/45? ACB sealed bearing upper 1.5 cromo external cup with caged ball bearing lower 188g ZS44/28.6|EC49/30 Black 188g 28.6 44/50 30 28.6 - 1.5 to 1-1/8`