Got my pass for the coach in my home state of Virginia. When registering the coach the menu choices included "Recreation Vehicles or Motor Homes". The sub group was further sub divided by axle count and tire count then further divided by under 7000 lbs. or over 7000 lbs. Ended up with a blue transponder just for the coach. No service fees but I did have to preload the account with $35 worth of toll fees.
I usually try and avoid toll roads if at all possible but when I can't having the pass makes the drive that much easier.