Super-smooth steering, quality materials, cutting-edge design and serious durability are all hallmarks of Cane Creek’s 40-Series headsets. – Technical Description: ZS49/30/H4/K – Bottom Type: ZS – ZeroStack – Bottom Head Tube Inside Dia.: 49.61mm – Crown Race Seat Dia.: 30.015mm – Crown Race Type: Steel, Face-Sealed – Bottom Stack Height: 4mm – Bottom Bearing Type: Black Oxide, Sealed – Material: 6061 aluminum – Weight: 58g