The 1591UBG is a beige, square 120 x 120 x 59 mm (4.72 x 4.72 x 2.32 in) enclosure in the 1591 Series of ABS multipurpose enclosures with card guides. The 1591U drawing lists it among the flame retardant ABS colour options alongside black, blue and grey, giving designers a lighter-toned housing for vertically mounted circuit boards.

It is molded from flame retardant ABS with a UL94 V-0 rating. Card guides molded into all side walls accept 1.5 mm (0.062") boards. Lap joint construction protects against dust and splashing water, and the enclosure is designed to meet IP54.

The drawing gives 120.00 x 120.00 x 59.00 mm overall and 113.54 x 113.54 x 54.90 mm inside, with card guides 49.90 mm high. The purchased assembly includes box, lid, 4 cover screws and pre-installed brass inserts; the lid accepts M3-0.5 machine screws, and the recommended cover screw torque is 35.5–42.5 ozf.in (25–30 cN.m).

The 1591UBG ships in shrink wrap with a shipping weight of 0.36 lbs (0.16 kg) and is RoHS and REACH compliant. The 1591UC clear flame retardant polycarbonate lid and 1591Z card adaptors are listed as accessories for the 1591U size.