The OTR 2-3/4" Hub Cap Window Kit is the perfect solution for inspecting wheel bearings without having to remove the hub caps. This kit includes a window, a gasket and a vent plug to help keep dirt and debris out and prevent moisture from building up inside the hub cap. The gasket helps to seal the window in place, while the vent plug helps to keep moisture out. With this kit, you can easily inspect the wheel bearings without having to remove the hub caps. FleetPride is your First Click in Heavy Duty®.