The 1551RFLBK combines the 50 x 50 x 20 mm 1551R body with a black ABS lid that has mounting flanges molded into it. The flanges bring the overall length to 66.30 mm (2.61 in), so the enclosure can be fixed to a wall or surface, or hung with a tie wrap, without extra brackets. Inside, a PC board up to 44 x 44 mm fits with an inside height of 15.98 mm.

The body is molded from general purpose ABS plastic with 2 mm (0.08 in) walls and carries a UL94 HB flame rating. Lap joint construction between box and lid protects against dust and splashing water, and the enclosure is designed to meet IP54. PC board mounting bosses are molded into the interior and accept #2 self-tapping screws. The black colour is specified as RAL 9011.

Outside, the 1551RFLBK measures 1.97 in x 1.97 in x 0.79 in (50 mm x 50 mm x 20 mm), with the length of 50 mm quoted not including the flange; overall length across the flanged lid is 66.30 mm [2.61 in]. Inside dimensions are 44.72 mm [1.76 in] long, 44.72 mm [1.76 in] wide and 15.98 mm [0.63 in] high. The maximum PC board size is 44 mm x 44 mm, and the shipping weight is 0.04 lbs (0.02 kg).

Each flanged assembly includes the box, the lid and 2 self-tapping #4 x 1/2" cover screws, black plated to match the enclosure; the recommended torque is 35-43 ozf.in (25-30 cN.m). Screws for securing the PC board are not included; the drawing lists part 1551ATS100 (#2 x 3/16" self-tapping (4.8 mm), pack of 100). The part is RoHS and REACH compliant and ships in a bag.

Hammond notes that some chemicals can damage or weaken ABS, including acetone, ketones, thread-locking compounds and cutting or tapping fluids, so check compatibility before cleaning or modifying. The enclosure can be factory modified (milling, drilling, printing) and solid models are available in .stp or .x_t format.