Below is a selection of Dust/Grease Caps for your trailer. These Grease Caps are installed in the outer face of your trailer Hub to protect your bearings from water, dirt, and road dust. They are also a method of keeping your Grease inside your Hub Cavity. For this reason it is very important that your dust cap always fits very snug onto your Hub. The Two Types of Grease Caps Shown (Both Different than Bearing Buddies, Red Eye Protectors, and XL Pro Lube System)