This sleek-looking 'button' is actually an ultrasonic sensor, ready for panel mount use. Inside is a module that uses high-frequency signals to determine distance to a surface. It's elegant looking and is more durable than the 'raw' ultrasonics we sell a lot of, so it would do well in a garage, robot, or installation where you want a durable dust and weather-resistant design. It has a range of 28 cm to 450 cm with a read resolution of 1mm (precision is 1 cm).