Summary: I lost the original stock eye cup from my Nikon D70s when I was Italy a couple of years ago. As expected, as this was a replacement part from Nikon, it fit perfectly. It appears to be constructed in the same quality as the original and has a snug fit. Because it's removable in order to clean it, be careful if you just sling your camera over your shoulder without a case (as I do) because you're likely to knock it off and leave it on the cobblestone streets of some...
Summary: This eyecup replaced a DK-21 I bought to replace the original on a D-70. The original lasted several years before falling off and getting lost. The DK-21 only made it a few months. This one seems like it may adhere better, even though it will be getting somewhat less use now that I have a D-300s.
Summary: Bought my D70 used and it came without an eyecup (apparently the factory D70 piece did not stay attached well and was easily lost). Ordered this as a replacement. It fits great, and physically snaps onto the camera body so it's not going anywhere.
Summary: I lost the original eyecup piece on my D40 last year because it just fell off by itself. I put it back on a few times but the last time it fell off without my noticing it. The manual states that the original eyepiece is the DK-16, but I didn't want to get another one that would have the same problem. The DK-20 is a great replacement eyecup for the D40 because it slides onto the lip found around the viewfinder and locks into place.