If you took the proven features and performance of the famous "KW" series antennas and added unique tuning mechanism to the top, you would own the equivalent of Firestik II, "FS" Series antenna. Aside from the ease of tuning, the patented design broadens the antennas bandwidth to keep SWR lower over more channels. The upper coil extension also increases the power handling capability of the antenna. All "FS" antennas are compatible with autos, trucks, vans, motorcycles and ATV's in single antenna configuration when metallic ground plane is available. Or, they may be used in dual (co-phased) configuration on any vehicle made from any type of material. Like all CB antennas, the "FS" antennas should be fine-tuned (SWR) in their final mounting location. If you have ever tuned non-tunable tip antenna, you will have real appreciation for the "FS" antennas. To tune "FS" antenna, you just pop-of the tip and turn the adjustment screw up or down as needed. All "FS" antennas exceed the requirements of any CB radio, new or old. Aside from the hi-performance loading coil that maximizes the transmit/receive functions of your CB, these top-loaded antennas will also receive the NOAA emergency weather alert and national weather broadcasts for radios with those features.