The unique design of our universal J Mounts allows you to get your TV antenna higher than standard 18" poles allow. These taller mounts are suited for most off air antennas and will attach to any flat surface including a roof, fascia, side of house, or deck rail. If you need extra elevation on your antenna, beyond the 3 - 4 foot length.
A:AnswerThe inside diameter of the STM1000 j mount is 1 3/8". It is important to know that we do not recommended extending the J mount as the mount base is not designed to take the extra weight. If extended, damage can be done to the mounting surface.