Crown style surface with stud mount. These wheel bearing covers come assembled with a low-profile stud permanently swaged into the bearing and replaces the need for a nut, bolt and spacer. Steel, stainless, shielded, and sealed bearing types available. Covers are made from a variety of materials: Corrosion resistant 303 stainless steel, abrasion resistant grey 70D urethane, thermal and chemical resistant blue nylon, general-use polyacetal, high strength PEEK with good resistance to high temperature and chemicals, general use 1045 steel with electroless plating.