I have three of these exact cans and love them. A couple of things....
1) They are rotomolded plastic and, like all rotomolded items, need a bit of trimming. Five minutes on the kitchen counter with a sharp knife and the extra material was trimmed away from the vent openings of all three cans, which is where they'll leak. I've run very rough terrain with them overfilled and stored on their sides. They DO NOT leak.
2) When upright they are exactly the same footprint and width as the 20-liter NATO cans I have for fuel, but they are a bit TALLER. I use the same 2-can rack that I built for the NATO cans. Note that they do bulge out when overfilled, but this is easily fine-tuned if needed. My NATO fuel cans fit my rack lying on their backs, but because the Rhino cans are taller, I have to stand them upright. See picture, below.
3) Yes, they are designed for interlocking and stack very nicely. When overfilled they don't really lock together that well because the sides bulge a fair amount. Still stackable, just not as well locked together.
I got them for a good price and find them very convenient. Here we had two of them on the roof where those NATO cans would go on trips to more remote areas; they fit the rack perfectly albeit standing up rather than lying on their backs. We had our girls with us so space was at a premium, as you can plainly tell!
