The 1591VSBK is an economy, general purpose ABS plastic enclosure in black, measuring 120 x 120 x 94 mm (4.72 x 4.72 x 3.7 in). It is aimed at designers and builders who want a square project box with integral card guides for vertical printed circuit board mounting, where a flame retardant material is not required. The taller 94 mm body gives generous headroom for stacked components and vertically mounted boards.

This economy version is molded from general purpose plastic (GPABS) with a UL94 HB flame rating and is not flame retardant; the flame retardant equivalent in the same colour is 1591VBK. The enclosure is designed to meet IP54, and lap joint construction helps keep out dust and splashing water. Black enclosures in the 1591 series come with black screws.

Inside dimensions are 113.23 x 113.23 mm (4.458 x 4.458 in) with an inside height of 89.90 mm (3.539 in). Card guides molded into all side walls accept 1.5 mm (0.062 in) boards and provide a guide height of 84.90 mm (3.343 in). For horizontal board mounting, 1591Z PC board card adaptors can be used.

The purchased assembly includes box, lid and 4 cover screws. On economy versions the lid is assembled with #4 self-tapping screws into fully plastic posts, with a recommended torque of 42-57 ozf.in (30-40 cN.m); replacement screws are 1591TS100 (silver) or 1591TS100BK (black). A 1591VC clear polycarbonate lid fits this size, and the 1591VSBK can be factory modified by milling, drilling or printing.