To protect the connection of feeder or feeder to antenna, easy to use, could be used for many times, more than 20 years life, for 1/2' ' feeder to 7/8' ' feeder, 1/2 feeder to antenna, 1/2' ' to 1 1/4' ' feeder, 1/2 feeder to 1 5/8' ' feeder or protect grounding connection for 7/8' ' feeder or 1 5/8' ' feeder. Foe more information, pls see the attachment.