Reducing Nipple 1/2" x 3/8" Male NPT 304 Stainless Steel Pipe Fitting .5": Industrial Pipe Fittings: Amazon.com: Industrial & Scientific
Southland 3/8 in. x 3 in. Galvanized Steel MPT Nipple 562-030HN - The Home Depot
Stainless Steel SS316 Hex Nipple, Pipe Fittings 3/8" Male Pipe NPT x 3/8" Male Pipe NPT, 6000 psi - Amazon.com
Amazon.com: Hooshing 3/8" Male to 3/8" Male NPT Hex Nipple Stainless Steel 304 Threaded Pipe Fittings for Brew Kit Home Piping, Pack of 4 : Industrial & Scientific