Originally posted by nostatic Nikon has it on the D300 and D700. And on the D300 it is really crappy - the one I saw in a local shop was unable to be reseated.
It's hard to tell, but from pictures, the Nikon covers
look a lot more "secure" -- they have little baffles and ridges near the edge of the opening, and seem to be pretty hefty, and made of a stiffish kind of rubber. The K-7 cover material looks a bit cheezier and more flexible, seems a bit thinner, and it just sort of wedges in the opening with nothing obvious to really provide any positive hold on it.
None of this means it doesn't work well in practice of course.
But still...