Panasonic KX-TGA551M 5.8 GHz Supplemental Handset for KX-TG5500 Series Telephone Systems (Metallic Grey) 5.8 GHz GigaRange frequency-hopping digital spread spectrum Supports caller ID and Call waiting, 50-call memory 1.4-inch full-color backlit LCD with 4,000-color display 5-hour talk time, up to 11-day standby battery life For use with KX-TG5561, KX-TG5566, KX-TG5571, KX-TG5576, and KX-TG5583 base stations