Design
Glance at the new 8in tablet and you might not immediately spot the subtle changes in its chassis. But just as Apple made the iPad Air 2 thinner than the original iPad Air, the mini 4 is now 18 percent thinner, a little taller and lighter.
203.2x134.8x6.1mm, 299g(+5g for cellular model)
While the old Smart Cover will physically fit, you really need one designed for the mini 4 because the magnets appear to have been repositioned and the old covers don’t connect as well.
Specific-fit cases for older iPad minis are unlikely to work with the mini 4 either. Apple hasn’t made a Smart Case for the new tablet, but you can pair the new iPhone-style silicone case with a Smart Cover to get all-round protection.
Mute switch
If you missed it on the Air 2, you’ll also miss the mute / lock rotation slider on the iPad mini 4, because it’s gone. Those settings are now only in the Control Centre which you get to by swiping up from the bottom of the screen.