10 flashing bulbs to make your lights flash. 2.5 Volt .425 Watt replacement Mini Bulb Indoor/outdoor Christmas tree flasher lights. Commonly used on 100 and 150 light strands, smaller strands usually use a higher voltage bulb. You can also put these bulbs in different styles of bases to make your light strand flash as long as the voltage and wattage is the same and your string uses the standard style of mini bulbs. There are many different base styles, please look at the pictures for a base D measurement diagram to make sure these are what your looking for. I also have other colors and styles of mini bulbs listed.