The best waterproof electrical distribution boxes are made from robust, weather-resistant materials such as polycarbonate or stainless steel. Polycarbonate boxes are particularly popular due to their light weight, high impact resistance, and excellent durability. NEMA stands for the National Electrical Manufacturers Association. These standards help users understand how well an enclosure protects against various environmental hazards. When this equipment is located outdoors, in a. Choosing a Waterproof Junction Box can make the difference between lasting protection and costly repairs. Take a look at the most common places where you need strong safety: Commonly mounted outside, exposed to dust particles and precipitation.