I had to look them up...yeah! I totally agree! Cut those puppies to fit your sleeves. I "frankenstein" ones all the time with scraps I am left with from vent covers. Totally works. I pop in a piece of cardboard with mine for structure. You can glue to that or back it with scotch tape (what I do).
I cut up the expensive 8 x 11 pages I had been using for another system. (way too heavy and the binders broke all the time) They are cool because they are rigid in their own right...and I just thought of something...I am going to try to hunt those back down and switch them out for my stamp/die sets as they hold cling on their backs. Cool!