Utility Outlet Box Extension Rings: Type - Utility High Voltage 347V Outlet Box; Material - Steel; Number of Gangs - 1; Height in inch - 4; Width in inch - 2-3/8; Depth in inch - 1-7/8; Capacity - cu-in - 16.5; Knockouts/Sides-Ends-Bottom - None-(2)1/2"-None