Cam bearings are not all created equal. Durabond bearings are the best choice for most builds, but there are situations where something different is called for. Clevite cam bearings are a little harder, and are generally a better choice for engines that will go through a lot of teardowns like a race car) or cam swaps. These are exclusive grooved cam bearings are made to our specs by durabond. They incorporate a groove around the outside too allow oil to flow around the second hole, which allows oil to enter the bearing on the loaded side, decreasing the chance of bearing failure due to high spring pressure. They also have an oil clearance closer to the middle of the factory spec, instead of tighter like the other off the shelf bearings, eliminating the need to clearance the bearings during assembly. If you have a problem with the cam bearings 'smearing', these bearings are the solution.