Transitions are custom fabricated from 20 gauge galvanized steel with welded construction. Flanges are not included but will be priced upon request.Transition Pricing: Price for a Transition is for fitting with square or rectangular end area approximately equal to round end area (within 10%). If Transition is not of equal area, take area of largest end in square inches, convert to a round diameter, and refer to chart for price. If square inch area is in between figures, round to closest diameter.Trans 3" Dia. to 11" Dia.: overall length = 9", S = 2"Trans 12" Dia. to 15" Dia.: overall length = 12", S = 2"Trans 16" Dia. to 24" Dia.: overall length = 16", S = 2"Please specify I.D. or O.D. dimensions.Pricing Example: 1. Trans #2 - A=10", B=12", C=12" Dia., A x B = 120 sq. in., C = 113.10 sq. in. Rectangle and Round is within 10%. Price for 12" Dia. Transition applies = $199.452. Trans #2, - A=11", B=12", C=6" Dia., A x B = 132 sq. in. Rectangle and Round is NOT within 10%. Take the largest area in square inches (132 sq. in.) and refer to chart. Price for a 13" Dia. Transition applies = $215.65Please allow five business days for fabrication.