Check the listing for details. 16 Light Keeper Pro Replacement Red C9 Bulbs For String Christmas Lights. Color: Red, Condition: New, Made in China. Listed at 4.89 USD. Add a pop of festive color to your holiday decor with these 16 red Light Keeper Pro replacement bulbs for C9 string lights. These durable and high-quality bulbs are perfect for indoor and outdoor use, and feature a corded power source for easy installation. Whether you're decorating your Christmas tree, mantel, or outdoor space, these bulbs will add a touch of holiday cheer. Made with a glass and metal material, these bulbs are designed to last throughout the holiday season and beyond. With a voltage of 120V, they offer a bright and warm ambience that is sure to impress your guests. Perfect for any occasion, these string lights have one setting and are sure to make any space feel cozy and inviting.