Popular commercial grade cords that are ETL or UL listed! These medium-base cords can interconnect via grounded plugs and sockets while maintaining the c/ETL/us safety rating for year-round use. The cords are used with Medium/E26 Base Bulbs. These commercial grade string lights are available in various colors and lengths with 24" socket spacing. The PVC sockets form a tight weatherproof seal around the bulb making them ideal for permanent, outdoor installations.