ULTRAGEL II® - a quality couplant which is specified in inspection standards. 

Ultrasonic Couplant is required for use with Ultrasonic Thickness Gauges and Ultrasonic Flaw Detectors.  The liquid couplant is to allow the transfer of ultrasound from the probe to the material under test.
 
This couplant comes supplied in 355ml bottles with a Material Safety Data Sheet provided.