Review (3/5): Doesn't fit my dryer, but duck tape works.
You get what you pay for.
My hair dryer measured perfectly inside the dimensions that supposedly fits. It arrived, and will not stay on.
I will give this 3 stars because it does fit right inside the barrel. Not in any way would it say on by itself, but a little duck tape later and this diffuser has worked well for me so far.
So if you don't need to take it on and off, and you don't mind the slightly redneck appearance of a duck taped dryer this could work for you.