The F4 series is the UHF radio that is, generally, in the GMRS and FRS frequency range, however there are UHF low (403-430mhz) and UHF high (430-470-ish), however it's unusual for a "civilian" to have UHF low since there are few, if any, frequencies to legally transmit on. FRS, GMRS and ham radio's 70cm band are in the UHF high range
The F3 series is VHF (130-ish to 175-ish), and the ham radio 2m band and MURS (public radios service) are in this range.