Roof Ventilator Base Adapter, Function Adapts 19-3/4 in Round Base to 24 in Square Base, Material Steel, Overall Width 24 in, For Round Base Diameter 19 3/4 in, Flange Height 1 3/4 in, Compatible Grainger Part Number 4HZ38, 4HZ39, 4HZ42, 4HZ43, 4HZ46, 4HZ47, 5DVL5, 5DVL6, 5DVL7, 5DVL8, 5DVP9, Finish Galvanized, For Fan Type Upblast Fans, Includes (6) Bolts, (6) Nuts, Metal Material Thickness 1.7 in