I bought this to see if it would work with my Markbass CMD121P - and it does the job perfectly well at a very reasonable price, pointing the bass at my face and not my feet and reducing direct contact with the floor - and it's foldable and slips right into the hollow at the back of the amp - or wherever. Admittedly, the combo isn't that heavy (just over 13 kg/29 lbs.), but I imagine it would take weightier things fine.
The wedge would seem to go well, then, with combos that are short and squat. I could see it working with squarish guitar amps too, but not with tall ones, like Fender Hotrods - or anything that is much taller than it is deep - gravity dictates that they would just fall over. I tried it with my Blues Deluxe - and it doesn't work - I also tried with Twin Reverb, and while it balanced without falling over, it just looked too much on the precarious side. But cube-type amps should work just fine.
So in my case and with its intended use for a squat combo, it definitely does the trick.