The RM5U1918SBK is an 18 in (457 mm) deep, 5U (8.75 in / 222 mm) high member of the RM rack-mount aluminum instrument enclosure series, 16.60 in (422 mm) wide with solid top and bottom panels. The extra depth over the 13 in model gives room for deeper circuit boards, transformers or instrument assemblies while keeping a sealed-looking top for equipment that does not need perforations.

The all-aluminum construction uses extruded side panels 0.125 in (3.2 mm) thick, extruded front and rear panels 0.125 in (3.2 mm) thick and flat top and bottom panels 0.064 in (1.6 mm) thick. The finish is a rugged textured black powder coat, so panels are not grounded to the frame; the grounding method is to be determined by the customer.

Overall dimensions are 8.75 in (222 mm) high x 16.60 in (422 mm) wide x 18.00 in (457 mm) deep, occupying 5 rack units. With the included pair of 19 in rack mounting flanges fitted, the drawing shows an overall width of 482.61 mm [19.000 in], with ear holes on 466.10 mm [18.350 in] centres. The front and rear panels measure 415.30 mm [16.350 in] wide by 221.49 mm [8.720 in] high, and handle mounting holes are provided for the 1427P1BK pull handle, available separately. Because it is 18 in deep, the RM5U1918SBK is listed with the RM5U18BRKT adjustable-depth rear bracket kit (sold in pairs), which adds up to 16.00 in (406 mm) of depth for 4-post rack mounting, so the rear of the chassis can be supported as well as the front.

The knockdown design ships unassembled. Each assembly includes 2 interchangeable front and rear panels, 2 interchangeable top and bottom panels, 2 interchangeable side panels, 4 self-adhesive rubber feet for desktop use, assembly hardware including screws and speed nuts, and 1 pair of 19 in rack mounting flanges with hardware. It is RoHS and REACH compliant and manufactured in North America; it can be factory modified (milling, drilling, printing), and STEP or IGES models are available.