We list here the BMD-3 and the BMD-4.
The differences are not that big, on the photos you can see the difference pretty easily: the BMD-3's top is round. the BMD-4's top is angeled.
The BMD-3 is one of the very few tanks that can be deployed from a plane in flight using parachutes... ok, the parachutes have to be really big (check the photos), but it works :).