I've been using them for at least a couple of years--all of mine are black. Have them on my D750, D610, D7100, and D90. The way the D90 cover was made, I don't like it, but they changed the design which is now much better.
The flap that goes in the flash mount comes out a lot. It isn't a secure fit so I simply reinsert it with no problem. If you have a grip, I don't think this will work since it wraps around the bottom slightly. I haven't used the tilt screen on my D750, but this does slightly cover the edges of the screen. No problems changing lenses (with the exception of the D90 which is why I don't care for that style).
Some of the buttons on the back (left) are covered, but there are icon impressions made into the silicone just like they are on the camera. The place where you move the focus point isn't covered so no problem changing that. The battery and card slots are easily accessible (not covered). The wheels (command and sub command dials) aren't covered so easy access to adjustments with no problem; however, they might take a little getting used. Although they aren't covered, the silicone is very close to the wheels. Therefore the wheels don't stick out as far as they would without the cover. No problem for me once I got used to it.
It's made of silicone and has a grippy texture to it. Overall I like them (with the exception of the D90 design) and will continue to buy them for future bodies.
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