Maxbotix LV-MaxSonar-EZ4 Sonar Range Finder MB1040.
This compact sonar range finder by Maxbotix detects objects from 0 to 6.45 m (21.2 ft) with a resolution of 2.5 cm (1") for distances beyond 15 cm (6"). Unlike other sonar range finders, the LV-MaxSonar has virtually no dead zone: it can detect even small objects up to and touching the front sensor face!The EZ0, EZ1, EZ2, EZ3, and EZ4 versions have progressively narrower beam angles.