Designed for use with nonmetallic sheathed cable in accordance with Article 370 of the 1990 National Electrical Code For Residential, Light Commercial, and Manufactured Housing Safe, non-metallic, non-conductive, PVC 3 zip mount retainers 18 cubic inch box 4 internal clamps Not suitable for fixture support 2-3/4 inch depth 3-1/2 inch diameter center to center