The 1591CTBU is an Ice Blue translucent polycarbonate enclosure in a 120 x 65 x 40 mm case with a deeper body than the 1591A and 1591B sizes. It fits circuit boards with blue or white LEDs, readouts or displays that need to be seen from outside the case.

The Ice Blue version is almost totally transparent to blue, white and near-white LEDs, readouts and displays, so status lights and indicators inside remain visible through the case. The case is molded from flame retardant translucent polycarbonate that is easy to machine, and lap joint construction between box and lid provides protection against access of dust and splashing water. It is designed to meet IP54 and is listed as RoHS and REACH compliant.

The drawing gives overall dimensions of 120.00 x 65.00 x 39.80 mm (4.724 x 2.559 x 1.567 in). The 35.90 mm inside height and 113.53 mm inside length leave room for taller components than the 1591A and 1591B sizes. Integral card guides accept 1.5 mm (0.062 in) PC cards, with a guide height of 30.91 mm and a slot width of 2.08 mm.

The purchased 1591CTBU assembly includes the box, lid, 4 cover screws and pre-installed brass inserts. The lid is secured with M3 x 10 mm Phillips machine screws threaded into integral brass bushings at a recommended torque of 42-57 ozf.in (30-40 cN.m); replacement screws are part number 1591MS100. The same size is also offered as 1591CTCL and 1591CTRD in the other translucent tints. Some chemicals can damage or weaken plastic, so check chemical compatibility before cleaning or modifying the case.