The 1590ZGRP121 is a near-square gray fiberglass enclosure measuring 122 mm x 120 mm x 90 mm (4.80 in x 4.72 in x 3.54 in) in the series ordering table. Its larger volume makes it a practical choice for electricians, OEMs and systems integrators housing larger components or square circuit boards in wet, dusty or corrosive locations.

The part data states the size as 120 mm x 121 mm x 91 mm (4.72 in x 4.78 in x 3.57 in) and the drawing shows 122.00 mm (4.80 in) by 120.00 mm (4.72 in) by 90.20 mm (3.55 in). The box is 65 mm deep and the lid 25 mm deep. Inside, the drawing gives 112.29 mm (4.42 in) length, 110.11 mm (4.33 in) width and 80.85 mm (3.18 in) height, and PC boards up to 108 mm x 107 mm fit.

The enclosure is molded from glass reinforced polyester with a smooth finish and heavy duty thick wall. It is C UL and UL listed under file #E65324, rated IP66, certified to NEMA 4, 4X standards per UL 508A (part data lists NEMA 1, 4, 4X, 12 and 13), UL94 V-0, and carries an IK09 impact rating in conformity with IEC62262. Recommended operating temperature is -40°C to +120°C (-40°F to +248°F).

This size steps up to M6 hardware: four self-captivated M6 - 1.0 x 30 mm stainless steel lid screws (recommended torque 8-9.5 lbf.in, 90-110 cN.m) compress an EPDM sponge rubber gasket, and the internal shelf accepts M6x1 screws for the optional 1590ZGRP121PL panel. Wall mounting holes sit outside the gasket channel. The 1590ZGRP121 includes box, lid, gasket and four cover screws and ships at 1.62 lbs (0.73 kg).