The WP Series Weatherproof Enclosures for Duct Smoke Detectors features 16-Gauge steel throughout, a drip-shield top, slip-on removable cover, and embossed mounting holes on back of enclosure. There are 3 knockouts in bottom of enclosure. Detector not included. Weatherproof rating is UL 50 type 3R / NEMA type 3R. Foam gaskets for sampling / exhaust holes, and all hardware included.