Designed specifically for a 2-1/2 x 11 ga. roller and to stay in the tube better than a plastic housed precision bearing. Highly recommended for high speeds and quiet operation. The hex adapter eliminates metal-to-metal contact between the bearing and axle which reduces noise during operation. Rubber contact seals on the internal radial bearing prevent dirt and debris from entering the bearing but increase rotational drag. Effective against small particle dust and debris. Recommended for high speed powered conveyor applications with moderate to light loads.