Confused on I Pass and Sun Pass etc--- toll roads ????

We have E-Z Pass transponders. One in the motorhome that is programmed for the motorhome and tow car. One in the car for the car alone. The one in the car is kept is a foil bag that it came in to avoid extra charge for the car when it is being towed. FYI, we got our transponders free from Mass. I don't know if they still offer them free. E-Z Pass works in whichever states participate in the program. We are very very happy with ours. We bypass long cash lines each trip.
Good luck,
Ron