Fits my ks88 mkii perfectly, even though it's technically 5 mm deeper than ks88es. The case itself is very sturdy and very well built - it already had its first test in a form of delivery, as the box it arrived in was torn and damaged as if the deliverers played ball with it for a couple of days, yet the case itself doesn't have a scratch.
As one of the reviewers already mentioned however, there is only a space for keyboard itself and no space for accessories. I have a couple of other points that this product could be improved on:
1. The handle is positioned to the side rather than the middle, so the keyboard hangs on one side when carrying and strains the wrist. It could have been easily avoided if the handle was just positioned in the middle
2. The closing hinges seem to be a bit misaligned, so when closing the case you have to shift the lid slightly to the side so that the catches can snap in place.