Wheel Bearing: 12 Bolt Rear "Worn Axle Bearing"READ THE FULL DESCRIPTION ON LHS LOWER PAGE: AXLE BEARING WITH SEAL BUILT IN Bearing size: OD 2. 578 Inch 65. 48mm ID is 3. 55346 41. 9mm It has a 12 bolt cover for GM (non BOP) diffs. This is what's used when you have normal wear in the rear axle caused by the normal positioned bearing wearing on the standard track area.. NOTHING COMPLICATED This will fit various 12 bolt GM rear ends, try and be sure this is what you need. Bearing size: OD 2. 578