Hi Lindsay,
They are constructed entirely of breathable fabric with the exception of the neoprene bootie, more layers around the lower leg to help with puncture resistance. If you are going to upgrade them then upgrade to the Sonic Seam wader, that is what I am in and what I have been in for a couple of seasons now. Found them to be very reliable indeed, light weight and superbly seamed. Only downside is that they are not as puncture resistant as some other waders but I would not recommend walking through anything in breathables that you would not walk through in bare legs anyway.
Cheers
Ben