Wheel Bearing Grease Packer quickly flushes out old grease and repacks the bearings with less the mess. The Wheel Bearing Grease Packer works on bearings up to 3 1/2" outer diameter. The grease stays in the tool cavity, not on your hands. To pack a bearing, simply place the bearing on the piston, press down on the cap until the old grease is forced out and the new grease shows on top of the bearing.