These bulbs have a C9/intermediate/E17 base. Use with C9 Cords or Commercial C9 Cords. Globe-shaped C9 bulbs, as well as the pointy-style Christmas bulbs, are a popular choice year-round for backyards, patios, party tents and other festive occasions. For a trendier look, our vintage, Edison-style C9 base replacement bulbs are a unique addition. C9 base light bulbs are used for decorative string lighting and is the perfect size for lighting smaller patio areas.