The Check Mate's design is based up SPO Medical's uniquely patented algorithms that use Reflective Pulse Oximetry Technology for accurate oximetry measurement. It also addresses problems typically associated with motion artifacts, ensuring accurate and reliable readings. The SPO 5500 Finger Pulse Oximeter is very small & lightweight. SPO 5500 measures blood oxygen saturation (%SpO2) and pulse rate SPO 5500 Finger Pulse Oximeter can be used by a variety of sports enthusiasts, including mountain climbers, hikers, skiers, bikers, and others interested in measuring blood oxygen saturation and pulse rate. Can be used outdoors in many conditions, including high altitudes, at high and low temperatures, and even in the dark. Ideal for home asthma monitoring requirements. Soft rubber boot sensor keeps it in place even while you are in motion. Battery Life Indicator Weight: 1.8 Oz. (50 Grams) including Battery Digital LCD display for SpO2 and pulse rate with BACKLIGHT SPO 5500 Finger Pulse Oximeter Includes: Lanyard Cord, 3.6v Lithium Battery 1/2 AA Size, Manual * Long-lasting battery - over 1,000 hours, using only a fraction of the power of conventional devices * Highly resistant to many forms of motion, reducing its susceptibility to the motion artifacts which typical pulse oximetry devices produce * Completely nail polish tolerant - no matter how dark the color * One year manufacturers warranty with 24/7 user support