Comes with weld on vent fittings for venting tank into frame. The caps are available in chrome or brass. For weld on applications only. Can be used for gas or oil tank. Machined out of mild steel for easy welding. O-Ring included. Weld in vent bungs are 1/8″ tapered pipe thread, which is standard for most oil fittings. 2″ width base fill spout base 2″ wide, 1-3/4″ height, inside diameter of 1-3/8″ with 2″ threaded cap.