These disc entrances are used on nucs and swarm traps making it very easy to transport your bees to a new location. By adjusting the door there are 4 possible entrances. 1. free flight2. closed3. queen excluder4. bumblebee excluder These discs are very convenient when transporting your bees. I would not be without one on my nucs or swarm traps. These discs are made of durable plastic and will last many years. IT COMES IN ORANGE OR YELLOW BUT NO CHOICE IN COLORS. It comes complete with a bolt and wing nut for mounting. They are 7 ½ inches in diameter. WHEN ASKED ABOUT WINTER KILL DO YOU WANT TO BE ABLE TO SAY “MY BEES DON’T DIE.” ARE YOU TIRED OF NOT GETTING HONEY? DO YOU WANT TO QUIT USING CHEMICALS ON YOUR HIVE WITHOUT YOUR BEES DYING? THEN WE RECOMMEND YOU PURCHASE OUR BOOK “RAISING HONEYBEES WITHOUT CHEMICALS” ALSO AVAILABLE ON EBAY. WE ALSO HAVE A WEB SITE http://www.chemicalfreebeekeeping.com AND WE ARE ON FACEBOOK AND YOUTUBE.