The Edelbrock Pipe Plugs help in filling up the unused holes in your Edelbrock intake manifold. The fitting size of this steel plug is 1/4 NPT (National Pipe Tapered Thread), male thread. These steel plugs have an internal allen head and a gloss black finish. They can be used to plug vacuum accessory holes in manifolds, fill plug holes in transmissions and rear ends, or any other spot that accepts a pipe plug.