Roof Ventilator Base Adapter Function Adapts 17-7/8 in Round Base to 19 in Square Base Material Steel Overall Width 19 in For Round Base Diameter 17 7/8 in Flange Height 1 3/4 in Compatible Grainger Part Number 5DVP1 5DVP3 5DVP5 5DVP7 Finish Galvanized For Fan Type Upblast Fans Includes (6) Bolts (6) Nuts Metal Material Thickness 1.7 in