The Enduro line of headset bearings begin with chromium steel, Black Oxide finish A/C type and then offer full 440C stainless steel at the top. They are always engineered with the largest balls possible and dual lip seals riding in a micro groove for ultimate protection against sweat and the elements. They are filled 90% with high pressure water proof grease, so you never have to guess if there is grease inside. Enduro Angular Contact (A/C) bearings, all balls are engaged to spread the force over a larger surface area, decreasing friction and minimizing wear.