Ok, I found the manual for the system I am buying on-line. On page 41 or a 50 page manual, it reads:
Aluminum Valve Stems & Galvanic Corrosion
Please note Minder Research makes two types of transmitters, the TM-2BRASS and the TM-2ALUM. The basic kits come with either 4 or 6 of the TM-Brass type transmitters. These will fit ALL Motor Homes (Class A, B or C), ALL 5th wheel trailers and ALL towables.
TIP: you ONLY need the special TM-2ALUM if you are towing a car or light
truck which already has a built in Tire Pressure Monitoring System (TPMS).
These will usually be 2007 or newer (as mandated).
These valve stems will be dull silver (vs. the shiny silver on your motor home).
The shiny ones are either stainless steel or chrome plated brass and do not require special transmitters.
Don’t bother with the “magnet test.” Most stainless steel is not magnetic.
What you are avoiding here is called “galvanic corrosion.” This happens when dissimilar metals come into contact for a period of time. Moisture (especially if salty) will cause the two metals to become so corroded that they cannot be separated.
Bottom line, the brass transmitters will work on any 5th wheel valve stem.