This 4-unit drop-in charging case is designed to store and charge up to 4 portable Listen FM products (LT-700, LR-300, LR-400 or LR-500) Place units in the slots, connect a charging cable to each unit, and they'll turn off automatically when fully charged. A power cable connects the case to a standard electrical outlet. It also has individual earphone storage slots to prevent cable tangling, and a large pocket to store the power supply, headsets, and/or additional items. The sleek, sturdy case has durable latches and includes a shoulder strap for easy transport. Use with NiMH batteries.