X-Rite has officially discontinued the ColorChecker Mini,
http://www.xrite.com/top_support.aspx?action=discontinued, which was 3.25 x 2.25 inches in size and came in a gray plastic slip cover, as Andrew noted. Instead X-Rite is including a "ColorChecker Classic (mini)" in the i1Profiler packages. This new "(mini)" is the same size as the ColorChecker Classic chart from the ColorChecker Passport, 4.25 x 2.5 inches, almost twice the size of the original Mini. The new "(mini)" comes in a paper slip cover.
To date, the new ColorChecker Classic (mini) has not been added to their product list so their is no way to order a replacement should you lose or trash it. The ColorChecker Proof, the new version of the ColorChecker Classic with a hole in each patch, used for print proofing, has also not been added to their product list. I assume that these omissions are an oversight on X-Rite's part, at least I hope so, for the user's sake.