TST 507 cons:
Small screen
Dim screen in bright light
Can't be turned off when USB cable is connected
Display graphic is OTR truck related. Would like a RV related graphics
All axles on a trailer use the same high/low psi settings (individual trailers can be different) and while OK for my toad there might be reasons for some toads or towed trailer to use different axle psi settings.
TST won't come clean on lower temperature readings than the actual internal tire psi, I called.
No explanation as to why they recommend not changing the axle temperature settings, perhaps related to the above.
Sensors are expensive $50
Pros:
It works well
Cap sensors are lighter but require removal for filling the tire, the lock nut is easy to loosen, stays on the stem and easy to retighten. Highly doubtful the nut would prevent theft
They claim rubber stems are OK but I suspect longer RV rubber stems would be a issue. My toad has TPMS and I have not found any metal stems with TPMS for it (for towing)
No problem with sensors on my toad as expeceted since multiple trailers are supported.
Sensor batteries are easy to replace
Note: There are older sensors that have a more involved lock mechanism and have 3 small screws for battery repacement. I don't have these so maybe someond can clarify.