When backed into the water for launching, boat trailer wheel hubs, heated by travel, are suddenly cooled. Air inside the hubs contracts and a vacuum is created. Water and dirt are sucked into the hubs through the inner seals and corrosion sets in immediately. Bearing failure can be expected within two seasons in fresh water - one season in salt water. When properly installed and maintained, Bearing Buddy prevents wheel bearing failure and eliminates bearing repacking. Boat trailer wheels can be completely submerged. Bearing Buddy also prevents bearing failure on motorcycle, utility, snowmobile, camping, and other trailers by eliminating moisture build-up in hubs and providing proper lubrication. A wheel hub does not have bearing protection unless a slight positive pressure is maintained inside the hub. If pressure is not maintained, water will enter and corrode bearings.. Specifications Dimension: 2.5" H x 4" W x 8.5" L; Weight: 0.96 lbs; .