I built my whole kit using 9AR on every tapered threaded fitting including fuel, brakes, oil and coolant and have had zero leaks for 740 hours; I like the stuff. However I recently used it up and bought the blue 85420 which I have not used yet. My understanding was the 9AR is no longer available and Kitfox factory has been selling the 85420. I always used the 9AR by putting it only on the male thread, but don't remember what the actual instructions on the tube said. I believe the 9AR was also described as a gasket/flange sealant rather than a thread sealant.

I understand from this forum that many folks have been using Loctite thread sealants on their projects with apparently good results (those thread sealants instruct you to apply only to the male thread). My own hesitation in using them is that they cure to a hard non-flexible condition which is fine for metal to metal fittings torqued to proper tightness. But for a metal fitting into fiberglass where the torque value is extremely low I want the non-hardening sealant that remains flexible and of course is compatible with ethanol containing fuel. My 2 cents.