Zinc Plated Replacement Accu-lube Dust Cap for Boat trailers or utility trailers. This dust cap is used if your axle is an Accu-lube axle with a grease fitting on the tip of the spindle. The Rubber plug easily removes to access your grease fitting. This dust cap measures 1.98 inches across and will fit most 4 and 5 Lug trailer hubs. Drive in installation ensures a tight fitment in your hub. For Easy installation, check out this 1.98 Trailer Dust Cap installation Tool.