The Arcadia Reptile " Ceramic Lamp Holder and Bracket PRO" is an easy-to-use and versatile lamp holder. Made from quality components this lamp can be used with most heat bulbs. (DO NOT USE WITH CERAMIC HEAT EMMITTERS inside your Toad Ranch Enclosure. Arcadia Deep Heat Projectors are a GREAT alternative to ceramic heat emitters!) * E26 USA Socket * included power cord comes with in-line on/off switch. * screws in easily into ceiling panel with Included (4) 1/2" * hangs down 3 3/4" from ceiling panel Don't know how many you need? Most 4' or larger enclosures require (2) These can be added to an already assembled enclosure if you discover you need another later. Just place your fixture into desired location and attach with the included screws. (be sure to not mount closer than 6" from any side wall & do not mount directly over a Cliff Hanger shelf) You will need to unscrew a few screws on the top panel of the enclosure to fit the cord through the cord slot hole if you do not have a grommet.