My little ones (both little and big are Karen Kay Buckley) have the hole, but not the BIG ones. I was considering punching a hole with my big pliers-type leather punch that is about 40 years old! I like that I can hang all the little ones up on my peg board and grab them in a second! (they look like plastic washers)
I bought a piece of heat resistent mylar and my DH punched circles of different sizes for me. My iron is very hot and I have not had a problem but it could just be that mine were made and the material used for the bought ones is different. I keep the circles in a little mint tin marked with what is in it. So far it has worked well. Oh, mine do not have a whole in the center either.
Gee, I didn't realize they would do that, Lynn. I got out the orignal directions (Karen Kay Buckley Perfect Circles) and it recommends using sizing and a medium-heat iron, leaving the iron in place long enough to dry the sizing. I admit, I was using a steam iron and the cotton setting for the small circles. My DGD made a large one to try out the process, and it came out fine, but I suspect the iron hadn't finished heating. It's good to know not to use a very hot iron!
This is a small suggestion that I wished I started doing sooner. I've been using those wonderful Mylar circles (you know, for Perfect Circles!) and I love the results. However, I was constantly misplacing the circle I was using! I would make the circles one at a time, taking out the mylar piece, pressing, then appliqueing the circle to the block... sometimes I will make several and put them aside to attach to the block at a later time, but nevertheless, there's "down time" for the mylar circle! My tip is this: simply pin the circle somewhere on your block when it's not in use! Run a pin through the fabric that peaks through the center of the circle. The circle will definitely stay put. I started doing that today, and it's been great! No hunting under fabric or under the table for that little circle!