The SP3 hineingepackt confirmed the first impression:
I would say on the side of 2-3cm, above 5cm too large.
Thus, the bag takes up much more space than is really needed and the SP3 is held not tidy. With cover that does not matter, as it very well adheres to the felt, without cover slips as stupid.
In the large envelope to the SP3 does not fit into the envisaged backpack with me.
Since the shell was explicitly touted for Surface Pro 3, it deserves in my eyes only one star: inappropriate.
(Probably for this reason, on the first product photo no Surface Pro 3 in his pocket)