FSA No.10 Headset for 50mm ID head tubes. Features a 1.1/8" steerer, alloy custom top cover, and \u00D85/32" x 20 retainer bearings. The headset has a headtube ID of 44mm for both top and bottom. The FSA NO.10 Threadless Headset is for 50mm OD head tubes and comes with an alloy custom top cover and 5/32"×20 retainer bearings. For 50mm OD head tube, 1.1/8" steerer, Alloy custom top cover, 5/32"×20 retainer bearings.