40-Series Zero Stack headsets set the standard for performance, durability and value. Drawing from the premium 110-Series design, the 40-Series includes all the features necessary for a durable, lightweight, long-lasting headset. Sealed ZN40 cartridge bearings. 6000 series alloy cups and materials. Steel crown race with integrated seals. Interlok spacer compatible. Item Specifications: Color: Black, Bearing Type: Cartridge, Crown Race: 30, Defined Color: Black, S.H.I.S Upper: ZS44, S.H.I.S. Stem Clamp Diameter: 28.6 Threadless, S.H.I.S Lower: ZS56,