What is the difference between these two TPMS systems.

The flow-throughs air up slower, and on toad wheels can be subject to damage from curb rubs. I also see more leak complaints with them. I removed the security shells from my 507 cap sensors, which makes them smaller, lighter, and less noticeable. It also means I remove them just like a standard valve cap to air up, just like you do with the flow-throughs. I've been running them like that on both the coach and toad for going on 5 years with no problems.