Let me tell you, cucumbers feel VERY good. The size of the inside of a hollowed out cucumber is perfect, at least for me. I thought it was going to be too narrow but it does have a little bit of stretch in it so it fits nice and tight. Also, since it's so tight it creates a very pleasurable suction once your fully inserted.
This one was a bit short since I didn't have a whole one to work with. I'll try to get some more pictures with a full one soon.