MB1340 XL-MaxSonar-AE4
High Performance Ultrasonic Rangefinder
Features of the MB1340, XL-MaxSonar-AE4, include centimeter resolution, has the highest noise tolerance and narrowest beam width of any sensor in the XL-MaxSonar-AE sensor line, short to long distance detection, range information from 20cm to 765cm, a 10Hz read rate, and various output options: analog envelope, analog voltage, and RS232 serial.
The MB1340 is a great choice for applications where only larger objects need to be detected.