Here's the manufacturer's web page:
Whirlpool® 0.5 cu. ft. Countertop Microwave with Add 30 Seconds Option
It has relatively small inside volume, but compared to a more typical microwave oven it is just a bit narrower and rounded off on the back corners, so it is just as deep as common microwaves (such as the same manufacturer's 0.7 cu. ft. Countertop Microwave
). To make it narrow and help it fit into a corner the working bits are under the cooking chamber (instead of to one side like almost every other microwave), so it is much taller than most. The narrowing and rounding makes sense (most stuff in microwave ovens is turned on a turntable, so the corners and extra width are useless), but wouldn't help it fit in the limited cabinet depth in a trailer, and the extra height makes it even worse for the limited height available.
I don't think this would work for an upper cabinet, but if someone is trying to stuff a microwave oven in a corner, this would be the one to use.