The replaceable buttons are the same part as the replaceable buttons on a few other remotes we make. To keep the cost of the button sets down, we include the same set with every remote that uses them.
Incidentally, it's possible to remove the buttons without opening the case, but it takes some very specific pressure at the side of the button. I've never done it myself, but I know several people at the office who can do it in seconds without damage to the button or the remote.
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