Keep water out with the White C9 Rubber O-Ring
Help protect your lights from moisture. These o-rings are designed primarily to be used in conjunction with LED retrofit bulbs installed in standard, traditional stringer wire. Snugging in around their narrower bases, these rings improve your light string's water resistance.
Place the ring around the base of the bulb. Then screw the bulb into the socket.
Make sure to fully tighten down your bulbs to ensure electrical contact between the bulb and C9 socket.