Bubble Lights Replacement Bulbs Set of 3 with C7 Base by Kurt Adler Set of 3 Bubble Lights Replacement Bulbs. For use in any indoor standard C-7 christmas set. C7 (Candelabra base) Indoor/Outdoor Use 120V 60Hz AC. Continuous bubbling when lighted. Cooler Burning Low energy lamps. By Kurt S. Adler, Inc. creators of renowned Christmas Decorations and Holiday Decor.