The size of this waterproof case is fine for small pop-out lens digital cameras, as long as they are no more than about an inch thick. The camera I used was eactly one inch thick, a little over 3.5 inches wide, and about 2.5 inches tall. The case can accommodate a slightly larger camera , but only VERY slightly larger. I say that because it can be difficult to position the camera correctly within the case if it's larger than these dimensions. Even with my camera, it took a few minutes' struggle to get the camera fully into the case and aligned with the lens socket because the plastic is very sticky on the camera body.
The plastic that the case is made from is completely waterproof, and the seal, despite looking inadequate, did the job nicely. Not a single leak anywhere. When I first got the case, I placed a piece of tissue within it, sealed it up and then submerged it in a sink full of water. I immediately got bubbles coming out of it from around the glass lens socket, which meant that water was coming in. I found later that it was leaking from that socket because it hadn't been fully tightened at the factory. So after twisting it down very firmly, my second such test resulted in no bubbles, and therefore, no leaks. Make sure the lens socket is very tight before you use the case, it will work. I think they made that lens socket in two parts so you can unscrew it to clean the glass more easily after use, which lakes sense, really. One more thing, make sure you peel off the protective plastic on the glass lens before use. I didn't notice it at first, but found it after my at-home water test. That could have caused my pictures to turn out quite blurry if I had left it on there. I did not take the camera very deep, only four feet or so, but it was completely submerged most of the time. I used it during a snorkeling session in the Caribbean, and I am impressed with its water-proof performance, but there are drawbacks. Read on.
The biggest difficulty I had with this case was the fact that it is essentially a bubble of air with a camera inside of it when it's in the water. What this amounts to is that when your camera is on and you're pointing it at something, you can't see the display screen on the back of the camera at all. Not only are you dealing with the air inside, but also with the daylight coming from above which illuminates that air to the point that the screen is invisible. You just have to point and hope you've got your subject in line with the lens for the picture. With a digital camera, that's not that big of a deal, because you can just shoot several photos of the same subject and erase the ones that didn't work. But it's still annoying to not see what you're pointing at, because maybe you need to zoom in or point further left, etc. As it is, you don't know until you look at the shots after the fact.
The other big drawback is that the socket where your pop-out lens slides into is a bit deeper than the lens when fully extended. (At least it was deeper than my lens) This causes you to get some part of that socket in many of the pictures, in the form of either a complete circle around your subject, or at least a curved edge on the right/top/left/bottom portion of the shot. I think I could have overcome that by manually pressing the front of the case against my camera to position the lens further into the socket, but as stated above, without seeing the display on the back of the camera, I had no idea I was getting that curve in the shot until I reviewed my pictures back on the boat. Again, as long as you're using a digital camera, you can erase the ones that don't work out, or you can zoom or crop the ones you like in order to eliminate that lens curve. My advice: use a nice high-resolution setting in your camera when using this case. That way, if you need to zoom or crop your shots, you'll have plenty of pixels to work with and will still have a very hi-def picture of the thing you were shooting.