Stainless Steel Wheel Bearing Protector The only sure way to prevent wheel bearing failure on a boat trailer is with the Stainless Steel Bearing Protector. Bearings fail when they get wet or dirty in the course of normal use. Even short distance trailering heats trailer hubs. When the hot hubs are submerged in water, the air inside them contracts, forming a vacuum which sucks water through the rear seals or around the dust caps. The water and attending grit will destroy the bearings. The Stainless Steel Bearing Protector keeps water and dirt from all trailer bearings, period. It simultaneously keeps bearings properly lubricated and extends their service life even when the trailer is subjected to moisture from outdoor storage or frequent submersion in saltwater or freshwater at boat launching ramps. The Protector is a stainless steel barrel that is pressed into the trailer wheel hub in place of the dust cap. Simply remove the dust cap, tap the protector into place (it's designed to self seat) and fill it with bearing grease. That's all there is to it! The hub is filled with grease through a grease fitting in the front of the bearing protector. As it fills with grease, an internal piston in the bearing protector moves forward to show the proper level has been reached. The protector even has an automatic pressure control to prevent overfilling and seal damage. Once installed and filled al you need to do is check the protectors grease level prior to submerging the trailer axles by simply pushing the piston. If the piston does not move or rock, top off the protector with bearing grease. Then, launch your boat with confidence. Certain models come with the blue Auto Check, a visual lubricant level indicator. Remember, when you've set your course on trailer-boatin fun, let Trailer Buddy Products help you keep your bearings.