Two aaa batteries power supply design: this pulse oximeter use 2 aaa batteries power supply, batteries Included in the package, which is convenient and fast, pls note our device have positive and negative signs in the battery slot, so when installing the battery, first be sure to check the positive and negative signs in the battery slot to avoid installation errors.This item for sports or aviation use only, not for medical use. Developed for children: this finger pulse oximeter fits for children's fingers , when you measure, your finger and body do not tremble during measuring, pls keep still, avoid measurement failure Accurate fast reading: you just need to clipping the children pulse oximeter on the finger, press power botton wait 8s, the spo2 and pulse rate measurement value will show on the oled display, automatically turn into the sleep mode in 10s without the opperation Portable design: the fingertip pulse oximeter made of soft silicone, makes it more comfortable, it is small in size and compact, allows you to bring the spo2 oximeter even when you are going out or traveling Pcakage comes with 1 pulse oximeter, 1 user manual, 2 aaa battery Fingertip Pulse Oximeter, Blood Oxygen Saturation Includes 2 × AAA Batteries. This item for sports or aviation use only, not for medical use.