This Trailer Buddy Bra is designed to fit the 2.441 or 2.717 Trailer buddies (6 or 8 bolt hubs). This cover slips over the end of your Trailer Buddy Bearing to help keep it clean and prevent grease from slinging all over your wheel. This Bra also is very helpful to keep the grease fitting and greasing area clear of dust and dirt. Using the Bra Cover on your Trailer Protectors will also assist in keeping the blue indicator ring free of dirt that could impact its performance. Common Question:Is the Trailer Bearing Buddy Bra necessary? Answer: While the Bra is not necessary for the Trailer Bearing Buddy to operate, the installation of the bra onto the Trailer Buddy will additionally keep dirt and grime from impacting the Grease Fitting. Also, this bra provides an extra moisture barrier.