Extra large differential fill and inspection cap. Designed to allow quick access for inspecting the ring gear. Features 1.5 inch diameter access hole. Threaded aluminum cap uses a rubber o-ring for a tight seal. Installation requires cutting a hole in to the top of the differential housing and welding on a threaded bung. Kit includes: one threaded bung, one cap and one o-ring. Plug kit can be ordered loose as a do-it your-self install or it can be ordered installed into a housing if you are ordering a housing at the same time.