The ER Series Insert Bearings have an inner ring that extends on both sides of the bearing to provide extra shaft support and a cylindrical OD. ER Series Insert Bearings are available in both 52100 Chrome Steel and 440C Stainless Steel. Chrome Steel Insert Bearings are harder than Stainless Steel and more durable in demanding applications. Stainless Steel 440C is resistant to corrosion from fresh water, steam, crude oil, gasoline, perspiration, alcohol, blood and food stuffs. Stainless Steel does contain some carbon so it is still slightly magnetic and may eventually rust.