Cane Creek AER Intergrated Short Cover Top Headset for 42mm Head-Tube, 1-1/8" Stem Clamp Diameter IS42/28.6 Black Top assembly only Pair with 110-Series bottom for complete headset Fits 1-1/8'' steerer tube tops (28.6mm stem clamp diameter) IS and Zero Stack versions available along with a new lightweight AER 10mm spacer