This is the HC-SR04 ultrasonic distance sensor. This economical sensor provides 2cm to 400cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm. Each HC-SR04 module includes an ultrasonic transmitter, a receiver and a control circuit. There are only four pins that you need to worry about on the HC-SR04: VCC (Power), Trig (Trigger), Echo (Receive), and GND (Ground). You will find this sensor very easy to set up and use for your next range-finding project! This sensor has additional control circuitry that can prevent inconsistent \"bouncy\" data depending on the application. **Features:** * Operating Voltage: 5V DC * Operating Current: 15mA * Measure Angle: 15° * Ranging Distance: 2cm - 4m **Documents:** * [Datasheet](https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf) * [Example Tutorial](http://www.instructables.com/id/Simple-Arduino-and-HC-SR04-Example/?ALLSTEPS) * [GitHub](https://github.com/sparkfun/HC-SR04_UltrasonicSensor)