The Stainless Steel Nipple SSM300x4, 3" MALE PIPE THREAD X 4" LONG PIPE NIPPLE 304 STAINLESS STEEL fitting is used to join two female threaded fittings together. The 3" MPT X 4" LONG NIPPLE is constructed of stainless steel 304 for higher corrosion resistance and use in many spraying and plumbing applications.