18" Antenna Extender - White. Constructed of high-quality reinforced fiberglass and finished to match Digital Antennas award-winning antennas, our antenna extenders are used to increase the height of an antenna to improve effective range or to place an antenna above on-board obstructions that may interfere with proper radiation.. All extenders mount standard 1"14 threaded mounts. Use a center brace when the combined length of your antenna and all extensions is more than 8'. Features:. Heavy duty fiberglass. Stainless steel ferrules. 1"14 threaded top and base. High gloss urethane finish. This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.