Close Pipe Nipple 1/2” 25 Pack NPT Steel Black Iron Gas Plumbing Fitting Sch-40. This pack includes 30 units of 1/2" pipe nipples in black iron steel. The NPT threading makes it suitable for gas plumbing applications. The Sch-40 designation indicates the thickness and strength of the fittings. Please note that the California Prop 65 Warning information should be checked with the manufacturer.