Screw base bulbs come in various sizes. The easiest way to measure what bulb you have is to measure the external thread base screw size. For example, an E26 bulb has a 26mm diameter, and is the most common style bulb used in residential applications. Available in 12 volt, 24 volt, or 36 volt, these bulbs are commonly found on large yachts and house boats. For marine applications, the incandescent versions are found in 25 watt, 50 watt, 75 watt, and 100 watt. The LED equivalents are usually approximately 3 watt, 5 watt, 7 watt and 9 watt. Cruiser LED also features a 7 watt bulb that can handle any voltage from 12 volt - 48 volts.