The SRF10 is the Worlds smallest dual transducer ultrasonic range-finder. This precision range finder has a range of  6cm to 6 meters and has an integrated I2C interface for easy interfacing.

A 5-Pin, 90 degree header is included with this product.

Features

Voltage - 5v only required
Current - 15mA Typ. 3mA Standby.
Frequency - 40KHz
Range - 6cm - 6m.
Max Analogue Gain - Variable 40 to 700 in 16 steps.
Connection - Standard I2C Bus.
Timing - Fully timed echo, freeing host controller of task.
Units - Range reported in uS, mm or inches.
Small Size - 32mm x 15mm x 10mm height.

Full Technical Data, and the sonar FAQ.