These are precision angular contact bearings, non-separable with outer rings relieved and available with 15 or 25 contact angles. For critical applications these bearings are stocked as universally ground duplex pairs with standard preloads and as single row bearings. A different design for separable, single row bearing series with inner ring relieved and 15 contact angle is also available. Duplex pairs can be mounted back-to-back, face-to-face or tandem depending on the loading expected. Due to high speeds, these bearings usually require phenolic retainers, which have either a stepped or cylindrical pocket design.