Please read before you make your purchase. If you are buying this for a mini bike please see photo #2 for measurement details. Type of material: mild steel, Uncoated Steel. Note:This header does not have any kind of paint. i can give it sandblasting if you want to paint it, I recommend rust oleum 2000F (you have to order it separately) send me a message in time to apply the sandblasting. Pipe Diameter. OD: 1.25" ID: 1 1/8" Tube with 0.83 wall. It has a 1" thread. Keep in mind that this type of common thread for water pipes or what they call black pipe is not the size of 1" the threads are measured by TPI, number of threads per inch. actual size is approximately 1.25" ID ...OD 1.50" 2 bolts included. 2 washers. Premium Gasket. -Engine not included. This been tested on Predator 8HP (301cc) OHV, Predator 13 HP (420cc) engine from harbor freight. -Works also: Hond_a GX240, 270 & 390, Briggs 1450 305cc, Lifan LF190F-BQ 15 HP 420cc, Made in U.S.A. Please do not order if your engine is not on this list.