The FSA Orbit Z headets feature a very low-profile design primarily for ATB and are compatible with Cane Creek internal style headsets. "Zero-Stack"/Cane Creek compatible. TH brand 36 degree Micro Angular Contact Bearings (red seal). 7075 alloy crown race. Very low profile designed primarily for Mountain Bikes. Patented alignment tip for increased durability and performance. Laser etched aluminum top cap. ZS49.57/28.6 (36x45) | ZS49.57/30 (36x45). Item Specifications: Color: Black, Weight: 89, Crown Race: 30, Bearing Type: Cartridge, Defined Color: Black, S.H.I.S Upper: ZS49, S.H.I.S Lower: ZS49, S.H.I.S. Stem Clamp Diameter: 28.6 Threadless,