The WH220 is a light-weight, single-ear, all-in-one wireless headset that operates in the 2.4GHz frequency range. This headset is used with DX100, DX121, DX200 and DX210 wireless systems. The WH220 uses the BAT50 Li-Ion Batteries and AC50 Battery Charger. WH220 Features: Two-channel 2.4GHz frequency range 3.5 kHz wide band audio Up to 15 beltpacks and/or all-in-one headsets on a single system Up to 12 hours of battery life