The new OM4 keeps the same foldable design as its predecessor, but it now comes with two magnetic mounts so you can quickly attach and detach your phone without needing to clamp it down and rebalance it between shoots. One magnetic mount is a clamp which wraps around your phone, while the second one attaches to the back of your phone and doubles as a finger ring so you can get a better grip with one hand. DJI says the new mount also has better tracking.
More specs and comparisons from DJI are here
