Standard Exhaust Stack An exhaust duct comes with a straight, 4-foot-long section, with one end corrugated for easy installation. All sizes are constructed from galvanized steel and require some assembly. You will need a Connector Ring if attaching to the booth fan Paint Spray Booth Exhaust stack components are fabricated from galvanized steel: 20 gauge for under 30" diameter; 18 gauge for 30" diameter and above. Available stack sizes are 12", 18", 24", 30", 34", and 42" diameters. Duct design meets Uniform Fire Code NFPA 91, latest edition. 4 feet long x Choose Diameter FOB - You will be contacted with a freight quote or you can arrange your own freight. Booth duct and accessories are custom made. They are non-returnable/sales are final once shipping is confirmed