These popular Commercial Grade String Lights are ETL or UL Listed! The medium-base cords can interconnect while maintaining the c/ETL/us safety rating for year-round use. Used with Medium/E26 base bulbs, commercial string lights provide the durability needed for long-term outdoor use. The C7 string lights provide a cost-effective solution for string lighting. C7 globe string lights are perfect for adding quick event lighting for parties or weddings, or just to add in small areas in the house, in the sunroom or around smaller patios.