Our 3 4 in 16 O ring to 1 8 in NPT adapter with 1 8 NPT plug is perfect for adding a pressure gauge port on multiple applications. The adapter is made from black anodized aluminum and the 1 8 NPT plug is produced from stainless steel. Fitting Style Adapter Fitting Category AN to NPT Fitting Angle Straight Fitting Material Aluminum Fitting Color Black anodized Fitting Size 1 8 AN Fitting Size 2 1 8 NPT