Boxes, Octagon Box Extension Ring, Appleton, Type: 4" With Knockouts, 1-1/2" Depth Inch, JB Bracket set flush, Gauging notches 3/8" and 1/2", Volume: 15.5 Cubic Inch, Side Knockouts: 4@1/2", Bottom Knockouts: 5@1/2", UL Standard: 514A, UL Listed: E2527