All bulbs are square pin (see picture on the right) The Current USA SmartPaq, 10,000K, 6,700K and 460nm Actinic bulbs are the exact same bulbs that were used in all Custom SeaLife fixtures. The SmartPaq is the equivalent of the SmartLamp. The 460nm Actinic is the equivalent of the Custom SeaLife Actinic (aka Ultra Actinic). We highly recommend using these bulbs for Custom SeaLife fixtures as well as Current USA fixtures and any other fixtures that take the square pin bulbs. Compact fluorescents are the same as power compacts (the "power compact" name was a Custom SeaLife trademark). These are the brightest bulbs on the market. ABOUT THE ACTINICS: The 420nm is a true actinic. the 460nm is bluer (less purple), and the 460nm is the bulb that Custom SeaLife used in their lights. The Current USA Orbits come with Dual Actinics, which are half 420nm and half 460nm. The difference is more aesthetic than functional (the animals will not care). ABOUT THE DAYLIGHT BULBS: The Dual Daylights are half 6,700K and half 10,000K. 40 watt Dual Actinic Lamp 420nm/460nm 16.75" x 1.75" x 1"