The best protection for your trailer bearings, the Bearing Buddy keeps water and dirt out of hubs and bearings. Easily installed, the Bearing Buddy has an internal piston that moves forward to show the proper grease level. Bearing Buddy measurement equals the distance between the outside of the bearing dust cap shoulders. Most hubs measure 1.98". Add the Bearing Buddy Bra (item #79619 sold separately) to keep grease off of the wheel. Sold in pairs.