The 40-Series is the workhorse of Cane Creek's headset lineup and incorporates all the features necessary for a durable, lightweight and long-lasting headset while offering the perfect balance of performance and value Contoured and relieved 6061T6 aluminum for minimized weight and maximized strength with split-lip sealed stainless steel bearings Low friction, dualseal crown race and top cover provides maximum sealing from contaminants, plus a captured compression ring design for carbon steerer compatibility (Interlok spacer compatible, sold separately) Cane Creek Integrated 41.0mm ID (36x45), Campy Hiddenset 42.0mm ID (45x45) , ZS (ZeroStack), or EC (traditional, External Cup) available for 1", 11/8" and tapered steerers Carbon indicates a carbon top cover on upper cup Internal parts are crosscompatible across the 10, 40 and 110 series