Jet Tech LLC exhaust tubes are double wall construction made to your required length and outside diameters to fit your applications. The inner tube dimension as well as the bellmouth size are determined by your turbine output and can not be changed very much due to mass airflow requirements of the turbine. The inner "hot" tube is .007 tempered 307 stainless steel with a welded or riveted on machined bellmouth. The outer "cooler" tube is .005 tempered 307 stainless steel. Typical mounting is with 2 tabs at the 3 and 9 O'clock positions and the supplied aluminum straps with #6-32 screws. Ehhaust Tube lengths can vary from a short few inches to the maximum length of 34". The tube shown in the photo is for the Ziroli Panther with a 22# thrust turbine measuring 19" long. Prices vary by size. Contact Jet Tech LLC via email at email@example.com for a quote and availability of your exhaust tube.