We have tested Sabine with a limited number of cases that we have in our possession. It really comes down to the material the case is made from. Sabine will cling to any smooth, hard, flat surface and most of the cases we tried did work.
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Sabine will grip any smooth, flat surface and will redirect sound for the original iPad. That being said, the curvature of the Sabine was specifically designed to match the contours of iPad2, the "New iPad", and the new "New iPad" (*shakes head at Apple's "new" naming convention* :)
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