Standard 3/8" x 24 Threads: Designed with a standard 3/8"-24 thread to fit most CB radio antennas, antenna mounts, compatible with Fire-stik style fiberglass antennas, mounts and accessories, Fit for 305311SS spring mount setups. Each spring is about 3.0" Stable Support for Long CB Antennas: Built to support compatible CB antennas up to 60 inches / 5 ft long while helping reduce vibration and road shock. The heavy duty spring provides a balance of flexibility and strength for fiberglass CB antennas and mobile radio antenna systems Heavy Duty Stainless Steel Build: Made from durable stainless steel with a polished finish to help resist rust, weather, and daily outdoor exposure. A reliable CB antenna spring mount for trucks, pickups, Jeeps, RVs, off-road vehicles, and other mobile radio antenna setups Helps Protect Antenna & Mount: The spring design allows the antenna to flex when it hits branches, garage doors, brush, or low-clearance obstacles, helping reduce stress on the antenna base and mount. Ideal for daily driving, highway use, trail riding, and work vehicles. Note:The antenna spring is heavy duty,but it can't guarantee that if it will be not flex when the speed is too fast , or if it will break down when the antenna being pushed or use it for some months ,importantly every person uses a different requirement,It may be springly、weak or stiff to you, but not the same to others.so please decide twice before you buy it - "Antenna spring, compatible with Fire-stik." This antenna spring was not created by Fire-stik. Multiple pack & color options for single replacement, dual antenna setups, backup parts, or fleet maintenance. A practical CB antenna spring replacement for drivers, installers, truck owners, and radio users who need dependable spare mounts Non original aftermarket part. The brand name and model designations mentioned above are used for purpose of demonstrating compatibility only.