Aquarius, pulse oximeters, Blue, features include easy to use - Clip on to finger and press the start button. You will get results within seconds. Easy to read - Large LCD display with readings, displayed facing the user. Accurate and sensitive - Get readings even if blood perfusion index is as low as 0.2%. Smart spring system - Self-adjusting finger chamber for a comfortable fit. Medical grade silicone - Non-toxic and hypoallergenic to finger. Infrared shielding - solid ABS plastic blocks 99% of ambient infrared. Low battery consumption with auto power-off feature. Light and portable - includes lanyard. SpO2 range: 70-99% (1% resolution). Pulse Rate Range: 30-240bpm (1bpm resolution). 2 AAA batteries (Not included)