Round polycarbonate, 4 in diameter, 12.5 cubic inch black non-metallic ceiling fan support saddle box, used in new work to mount a ceiling fan or heavy light lixture from ceiling. Suppports a 70 pound fan, or fixture. Unique saddle design straddles standard joist. Hands free installation. 1/2 in setback. 2 knock outs 1/2 in each on the side. 4 cable clamps, mounting hardware, instructions, and high strength, hardened screws included. 2-hour fire rating, UL Orange Book.