The Featherbrite LED UV bulb is most beneficial for your bird when used with the 5500k LED full spectrum daytime bulb. Both the LED full spectrum day bulb and the LED UV bulb used together is 8% UVA and .04% UVB which simulates sunshine. We have assembled a kit for your bird with both bulbs PLUS a standard light socket adapter for the candelabra base UV bulb. The FeatherBrite 6w LED full spectrum bulb will fit any standard socket. The FeatherBrite UV bulb has a candelabra base. This NEW Featherbrite LED Bulbs package includes the following: * (1) 6W Sunshine Full Spectrum daytime bulb 5500k 6W – no heat and does NOT contain any mercury. It does not contain any UV * (1) 1.5w low dose uvb Bulb. 660 lumens (like a 60w incandescent bulb or 18w cfl bulb) and a rated life of 30,000 hours. Also the kit includes (1) socket adapter for the candelabra UV bulb and a duel socket Y for both bulbs. Recommend replacing bulbs annually as some of the LED bulbs can dull. The low-dose UV LED Bulb can be left on 24 hours with no concern whether your pet is getting too much UV. Large bulb – 5 ½“wide 4 ¾” long Small bulb - 1 ¾” wide 3 ¼” Long