The 1551FFLBK is a black ABS plastic miniature hand held enclosure with a mounting flange molded into the lid, measuring 50 x 35 x 15 mm (length not including flange, depth including lid). Hammond's 1551 series is ideally suited for mounting small printed circuit boards or for use as potting boxes, and the flanged lid makes the 1551FFLBK well suited to wall mounting or suspending with a tie wrap. It is aimed at electronics designers, OEM engineers and hobbyists housing compact sensors, transmitters and control boards.

The box and lid are molded from general purpose ABS plastic rated UL94 HB, in black (RAL 9011 per the drawing; the part page lists the colour as Black). Walls are 2 mm (0.08 in) thick, and lap joint construction provides protection against access of dust and splashing water; the enclosure is designed to meet IP54. PC board mounting bosses are molded into the box and accept #2 self-tapping screws.

Inside, the drawing gives 45.17 mm (1.78 in) length, 30.17 mm (1.19 in) width and 11.00 mm (.43 in) height, with a maximum P.C. board size of 44.50 x 29.50 mm (1.75 x 1.16 in). Overall length including the flange is 67.30 mm (2.65 in). Shipping weight is 0.04 lbs (0.02 kg).

The purchased assembly includes box, lid and 2 cover screws. Lid screws are #4 x 1/2 in self-tapping, colour matched (black plated with black enclosures); replacements are 1591TS100BK (black, pack of 100). PC board screws (#2 x 3/16 in self-tapping, 1551ATS100, pack of 100) are not included. Recommended torque is 35-43 ozf.in (25-30 cN.m). The 1551FFLBK is RoHS and REACH compliant; the same size is also offered as 1551FFLGY (gray).