This boat trailer bearing buddy bra cover is designed to fit the 1.980 bearing buddies (fits most 4 lug or 5 lug trailer hubs). This is part number 19B. This cover slips over the end of your bearing buddy to help keep it clean and prevent grease from slinging all over your wheel. If you are unsure of the size bra you need to go over your Trailer Bearing Protector, you should revert to the side of your Protector, looking for the 1.98" Size. This is the standard size for most 4 Lug and 5 Lug Hubs, so it would be uncommon for you to use a different size on a 4 Lug or 5 Lug Wheel. In order to ensure that your Bearing Protector remains easily accessed and functional, using a Bra on top will keep both the grease fitting and blue indicator ring free of dirt and debris.