From the leaders in pulse oximetry, the ISPO2 pulse Oximeter allows you to noninvasively track and trend blood oxygenation (SpO2), pulse rate (PR), and perfusion index (PI) - even during movement and low blood flow to the finger. With the free Masimo ISPO2 application, you can graphically view your SpO2 and PR measurement history over time and share that data through email. The ISPO2 features the same Masimo SET technology found in hospitals worldwide. The ISPO2 will be useful to anyone interested in measuring blood oxygen and pulse rate, such as hikers and climbers, as well as pilots and passengers. Not intended for medical use. SIZING: For sizing, we recommend the Large size for people over 66 pounds. The Small size is recommended for those under 110 pounds. If you are between 66 and 110 pounds, we recommend the Small size if you have slender fingers.