1" Common male Pipe Thread...1" does not mean the actual size of the adapter... read at the bottom of the page to understand how to measure threads. Each thread size has a defined number of threads per inch (TPI). You will receive 2 adapters including the premium hardware for installation. 1" NPT male thread, Exhaust Flange is Mild steel, the rest is 304 stainless steel, top notch Tig welded. 2 stainless steel screws + 2 Lock washer. high quality Exhaust gasket, Good for: Mini bikes, go karts, generators... multipurpose. This been tested on: Predator 670 V-TWIN, Predator Max 459, DuroMa XP16HPE 420, DuroMa XP18HPE 457, Predator 8HP (301cc) OHV, Predator 13 HP (420) Engine from harbor freight. -Works also: GX Hond 240, 270 & 390, Briggs 1450 305cc, Lifan LF190F-BQ 15 HP 420cc. Made in U.S.A. Engine does not include! This part is designed only for use on the Exhaust port side only... Does not work as intake manifold***Finding the Correct Pipe Thread Size National Pipe Threads Pipe sizes do refer to physical dimensions, but the plumbing industry standard for the sizes of pipe is not always as straight-forward as measuring the pipe. Measuring the pipe will oftentimes mislead you into choosing the wrong pipe, so do take care. The "pipe thread size" as shown in column 3 of the table below is measured and based on the inside of the pipe. But, to actually determine the size of a pipe, the outside diameter of each pipe or fitting must be measured and compared to the table for size identification. For example, a 3/4" NPT pipe thread has an outside diameter of 1.050 inches. Each thread size has a defined number of threads per inch (TPI). The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI (threads per inch) and OD (outside diameter) of the thread are required for positive identification of thread size because several sizes have the same TPI.