SQUARE BOX EXTENSION RING TYPE; PRE-GALVANIZED WELDED STEEL MATERIAL; 4 INCH; 4 INCH; 1-1/2 INCH; UL APPROVAL; 50 STANDARD PACKAGE; 21 CU INCH CAPACITY; (8) 1/2 INCH SIDES, (4) 3/4 INCH SIDES KNOCKOUT SIZE; 12 KNOCKOUT(S); BOWERS[R] BRAND; SHAPE SQUARE