Features: brand new and high quality A pulse oximeter measures the oxygen saturation in the bloodstream. Since blood oxygen saturation can reflect early medical problems such as heart and lungs, this reading is very useful as a general health monitoring metric.Its working principle is based on the light-absorbing properties of hemoglobin in the blood. Oxyhemoglobin absorbs more infrared light than red light, while deoxyhemoglobin absorbs more red light than infrared light. Therefore, the red and infrared LEDs in the oximeter alternately emit light, and the photodiodes receive the light signal that is not absorbed. The ratio of red and infrared light received by the photodiode is used to calculate the percentage of oxygen in the blood. According to the pulsatile nature of the arterial blood flow, the pulse rate and intensity are also determined and displayed during the measurement. Optical sensor: IR and red LED combined with photodetector. Measures absorbance of pulsing blood. I2C interface plus INT pin. 3.3V-5V power supply. Specifications: Material: ABS Length: approx. 3cm/1.18in Package Includes: 1 x Heart Rate Oxygen Concentration Sensor note: No retail package. Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!