CB antenna manufacturers are not very good about advertising the wavelength of their antennas, and it can make a huge difference. Lots of cb antennas are 5/8-wave because they have more gain than others, but they need a good ground plane to tune-up with acceptable SWR and they don't always tell you that. If you're mounting it on your roof or hood, there is usually a plenty good ground plane there but if you're mounting it on a bumper, spare tire, or tailgate hinge there probably won't be. In those locations, a 1/2-wave antenna is a much better choice as they don't require a good ground plane. Even though they're not advertised that way, I have found from experience that the Firestik Firefly and the Wilson Flex antennas are 1/2-wave and will tune up in locations that 5/8-wave antennas will not.