2-1/2" x 6" Nipple, Stainless Steel Sch 80 Threaded Both Ends (TBE) 316L NPT2 1 2" x 6" Pipe Nipple, Stainless Steel Schedule 80 Threaded Both Ends (TBE) 316 316L SS NPT The Nipple Threads are National Pipe Thread (NPT), also known as American National Standard Taper Pipe Thread. This is the common thread used for threaded pipe connections in the United States. NPT is defined by ANSI ASME standard B1. 20. 1