4tronix HC-SR04 Ultrasonic Distance Sensor V2

4tronix Robo:Bit for BBC micro:bit and Accessories - 4tronix RBITSON, When used with the Robo:Bit buggy the Ultrasonic Distance Sensor lets the robot detect objects before it collides with them allowing you to program it to avoid them. It can also be used to create a 'follow me' program where the robot tries to stay a certain distance from the object in front of it. 4tronix HC-SR04 Ultrasonic Distance Sensor V2

Price: 4.79 from Rapid Online Rapid Electronics Ltd.