The purpose of trailer bearing protectors is right in the name: They protect the bearings by keeping foreign particles and water out. But why pay for additional towing equipment if bearings are cheap and easy to replace?
Without this protective equipment, you'll need to replace tow bearings as often as once a year, due to wear from road debris and grease that has washed away while launching a boat. This will cost about $15 to $25 for a complete kit, not including your time (if you're handy with hubs and bearings) or the cost of labor at the local mechanic's shop. Kits generally include enough to repair only one hub: two bearings, two races for the bearings to roll against, one grease seal, and one cotter pin.
Bearing protectors can be found for between $20 and $40, plus a few dollars for the bras to keep them clean. Bearing protectors can keep bearings greased and free of debris and water for years, making it more cost-effective to protect bearings than to replace the hubs or bearings periodically.
For more information on trailer bearing protectors, please see the links on the next page.