Large size base, 18" x 18", to comply with Kentucky code. 4" pipe size. Exclusive 1-piece construction insures a positive leakproof installation every time. Elastomeric collar allows the vent stack plenty of room for expansion and contraction. Galvanized base is made from 24-gauge deep drawing steel extra high with no seams. Easy-to-install, the flashing slips over the vent stack and automatically adjusts to pipe size and roof angle, and remains perfectly flat on the roof.