A standard light bulb base is typically a medium screw-in base, also known as E26 or E27. This is the most common base used in lamps and fixtures for traditional 60-watt incandescent bulbs. LED equivalents work just fine in any of these bases, and have a lot of cost-benefit. The candelabra base, E12, is a smaller screw-in base that is typically used in chandeliers and ceiling fans. The intermediate base, E17, is used in appliances and old Christmas lights. The mogul base, E39, is found on higher wattage incandescent and HID bulbs.