40KHz Ultrasonic ranging module. Designed for incorporation in equipment, robots etc. Used to determine the distance to a target. Features high accuracy, non-contact, stable measurements in a simple 4 connection +5VDC module. Module “Pings” a target when triggered then outputs a logic pulse proportional to the distance.
Power: 5VDC
Range: ~2cm-~2.5m
Resolution: >0.5cm
L: 1-3/4" W: 7/8" HT: 5/8" WT: .02
These are $3.95 at https://www.mpja.com/HC-SR04-Ultrasonic-Ranging-for-Arduino/productinfo/19605+UT/
I have been doing business with MPJA for several years now, and they have always done a good job.