The 1551PTBU is a square 40 x 40 x 20 mm enclosure molded in translucent blue general purpose ABS. It is ideally suited to mounting small printed circuit boards or potting compact assemblies, with a translucent blue body instead of the opaque black or grey offered in the same size.

The enclosure consists of a box and lid joined by a lap joint, protecting against dust and splashing water, and it is designed to meet IP54. The ABS is UL94 HB flame rated, and walls are 2 mm (0.08 in) thick.

With the lid on, the 1551PTBU measures 1.57 x 1.57 x 0.79 in (40 x 40 x 20 mm). Inside there is 34.72 x 34.72 mm of space and 16.00 mm of height, taking a P.C. board up to 34 x 34 mm. Standoffs molded into the interior accept #2 x 3/16 in self-tapping screws, sold separately as 1551ATS100.

Each unit includes box, lid and 2 black plated #4 x 1/2 in self-tapping cover screws (black plated screws are paired with blue enclosures); recommended torque is 35-43 ozf.in (25-30 cN.m). It is RoHS and REACH compliant and ships in a bag at 0.04 lbs (0.02 kg).