Cane Creek AER II Series Headset Bearing - Blue - Steel-Aluminium - 1 1-8 Inch - 30.15x41x6.5mm - 36x45 - IS41Genuine Cane Creek AER II Bearing. Made from Steel and Aluminium for the lightest possible bearing. Even though it manages to shave a whopping 35% off the weight of a standard bearing, it still maintains the quality and durability that Cane Creek bearings have become known for. The best part is, these are cross compatible between all of Cane Creek's other headsets! So you can upgrade your Ten, Forty or 110 series headset to have AER II bearings.