Originally Posted by
tenngal
They are rarely sized correctly, unfortunately.
I'm afraid that the words "rarely sized correctly" aren't fair, in my experience at least.
I have only had incorrectly-sized squares with one really cheap knock-off package of 10" squares, and the squares were over-sized in that case. Plus, on the package was a warning that there might be some slight size discrepancies, so I considered that I had been forewarned.
All of the name-brand pre-cuts I have, and I have had quite a few, have been fine, with no size problems whatsoever. If you come across a cutting mistake, contact the manufacturers. I'm sure they'll want to know because their reputations are at stake.