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