The L250R features a display unit with superior sound quality, extended battery life, enhanced probe sensitivity, interchangeable probes, and a . The large informative display shows battery life, signal quality, and extended 50 to 220 bpm heart rate. It includes a charging system where you don't have to worry about overcharging or draining the batteries. Main Unit-Includes One Probe of Your Choice. Probe Choice: 2MHz & 3MHz obstetrical 4,5 & 8 MHz-vascular.