My grades depend on what is important to me. Important things: The M-type coupling connects perfectly with the ARB (CKMTA12) dual air compressor, completely leak-free with PTFE tape. The air hose is connected to a coupling and an M plug using compression fittings. The whole system is virtually leak free when properly assembled, which is very simple. Everything I've mentioned so far seems well made and high quality, but only time will tell the rest. What doesn't matter (at least for me): I…