The economical Atlas Sound 221-18 cabinet is 22 5/16" wide, 18 1/2" deep, and contains 21RU vertical panel spaces. The 221-18 cabinet includes one pair of 11 ga. CRS adjustable mounting rails.The series is constructed of 16 ga. CRS and include base, top panel, side panels, mounting rails, a removable rear door with cylinder lock and flush door pull handle.Offers several installer-friendly advantages, including an expanded 6RU opening in the cabinet top and bottom which can be left open for wire access and/or ventilation, or closed using a standard vent or solid panels.Rear doors (included with all models) are hung with quick-release spring hinges which allow them to be rotated 180° for right or left-hand opening. If a front door is ordered, it will be keyed differently than the rear door for security.