The Fingertip Pulse Oximeter by Drive is super compact and light, weighing only 50g with batteries. It uses low power and automatically powers off. Comes complete with low voltage indicator. Uses convenient AAA alkaline or rechargeable batteries. Measurement accuracy: Meaningless when stage being smaller than 50%,+/-2BPM. For pulse rate Measurement Performance Oxyhemoglobin and pulse value can be shown correctly when in low perfusion: pulse-filling Rate is 0.5%. Interference Resistance Capacity Deviation is smaller than+/-1% between value of Oxyhemoglobin against Ambient Light: measured in natural lighting indoor condition and present lighting sources and that measured in a dark room. Compact and Light Design. Convenient AAA size alkaline or rechargeable batteries Low power consumption and automatic power-off design Low voltage indicator