Numis Products Coin "Tubes" (square outside, round inside)

I bought some of these, but I'm second guessing myself on using them.
The plastic feels "soft" and I wonder if they are safe for long term storage.
Anyone with knowledge and experience care to comment???
Current maintainer of Stone's Master List of Favorite Websites // My BST transactions
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www.brunkauctions.com
The only thing I could complain about is some (but not most) have a little bump inside the bottom that might touch the center of the bottom coin. I'm assuming they might have fixed it on the newer ones.