The 1551MTBU is a 35 x 35 x 20 mm square enclosure molded in translucent blue general purpose ABS plastic. It is sized for very small printed circuit boards and potting jobs, and the translucent blue finish gives a distinctive look compared with the black and grey versions of the same size.

The enclosure is built from a box and lid that close on a lap joint, protecting against dust and splashing water; it is designed to meet IP54. The ABS carries a UL94 HB flame rating, and walls are 2 mm (0.08 in) thick.

Outside, the 1551MTBU measures 1.38 x 1.38 x 0.79 in (35 x 35 x 20 mm) with the lid on. The inside cavity is 29.73 x 29.73 mm and 16.00 mm high, and the largest P.C. board it takes is 29 x 29 mm. Molded standoffs accept #2 x 3/16 in self-tapping screws, sold separately as 1551ATS100.

Included are the box, lid and 2 black plated #4 x 1/2 in self-tapping cover screws (black plated screws accompany blue enclosures), torqued to 35-43 ozf.in (25-30 cN.m). It is RoHS and REACH compliant, ships in a bag and weighs 0.03 lbs (0.01 kg).