Attributes . (1) 5/16 Inch, (1) 1/2 Inch, (2) 1/2 Inch-3/4 Inch-1 Inch-1-1/4 Inch-1-1/2 Inch-2 Inch-2-1/2 Inch Concentric Knockout, 1 Inch-1-1/4 Inch-1-1/2 Inch-2 Inch-2-1/2 Inch Concentric Knockout (Bottom) . Names