Depending on how you use it, this is either a godsend or a waste of money.
If you plan to use it with a pressurized gas canister based stove, it’s pretty useless because the height of the wall is just too low. With most of these setups, the stove portion fits on top of the gas canister so right there, the flame is above the reflector wall. no stars for this use.
If you use it with a multi-fuel stove, it’s a little better. Most multi-fuel stoves use a cable to run to the fuel (pressurized gas or primer pump based liquid fuels), so the stove is considerably lower. When setting a cup or pot on the stove, the base is about a centimeter or two below the wall, so you should get a little help there. Two stars for this use
If you’re planning on combining this with a tiny esbit emergency stove, than this is a true godsend. those tiny stoves have 2 wind protection walls already, but they don’t work real well in even slightly windy conditions. So having this will be a noticeable help in efficiency. Three stars for this use.
If you’re building a small wood fire in a breezy condition, than this is a five star tool. You can create a small wind shield that will protect against wind at the earliest stages of getting a fire going and then use your breath to feed oxygen to the embers and early fire in a controlled manner. Great tool for novices like me. Five stars for this use!
All in all, I’d say this is good in an emergency kit or on an ultralight camping trip, but likely wouldn’t use it otherwise.