This fingertip heart rate monitor continuously displays your resting pulse without relying on uncomfortable chest straps or requiring you to press a button. The device simply clips to your finger and automatically provides an EKG accurate reading to ±2 beats-per-minute. It displays readings on a 1 1/3" LED screen using large, easy-to-read numbers. The unobtrusive heart rate monitor fits in a shirt pocket for ease of portability and it won't inhibit hand movements when in use. The device also measures your blood's oxygen saturation (SPO2) without requiring a doctor's visit or a blood sample. Requires two AAA batteries. 2 1/4" L x 1 1/4" W x 1 1/4" H. (2 oz.)