Aluminum construction For tapered 50mm/57mm head tube 1-1/8 alloy internal cup with 36?/45? ACB sealed bearing upper 1.5 alloy external cup with 36?/45? ACB sealed 1.5 bearing lower 141g ZS44/28.6|EC49/40 Black 141g 28.6 44/50 40 30.3 - 1-1/8 to 1.5`UPC/EAN/GTIN: 400310030771