Ultrasonic Distance Sensor from eBay

 
HC-SR04 Ultrasonic Sensor Distance Measuring Module from czb6721960 shop on eBay $1.58 USD.
item #140717531874
 
Ultrasonic range finder Distance Sensor from eBay
 
Ultrasonic range finder Distance Sensor from eBay
 
Ultrasonic range finder Distance Sensor from eBay