Manual Station Weatherproof Back Box (red). A red cast-metal weatherproof back box measuring 4.75 in. x 3.25 in. x 2.25 in. (12 cm x 8.3 cm x 5.7 cm) with ½ inch (12.7 mm) knockouts in the short sides. The back box is UL listed under UL38 and is UL certified for use in Canada. It has a NEMA rating of 3R and an environmental protection category of IP54.