-8AN Male to 3/8" NPT Male Union Adapter Fitting with 1/8" NPT Port. Vibrant Performance pressure gauge adapter fittings are designed to mount inline on your fuel feed line. They feature an 1/8 in. NPT port made for a fuel pressure gauge to thread into. The fittings are made from high quality aluminum and then black anodized for protection. Available in different sizes and styles, these Vibrant Performance pressure gauge adapter fittings will have you reading fuel pressure in no time!