The FAA have never been known for their speed in updating documents, and this goes for the circulars that control airport friction testing. The RT3® Flight Friction Tester was approved in May 2010. One day, we hope that the FAA will find time to update us into the circular, but until then, here is their letter of approval.
Also, the RT3® Flight and Water System is AIP eligible. It is designed and manufactured here Plain City Ohio. Where possible we source parts from the USA. Our US content is very high.