With smart bulbs, you can smarten up any existing light fixture; they’re great for single-bulb fixtures or groups of light fixtures you’d like to smarten or make more colorful. In addition, smart light bulbs can be used in any fixture where a regular bulb was previously used as long as the bulb’s base matches the socket size of the fixture. Smart bulbs are not made for every socket size, but the most common sizes are available, including E12 and E26.