Doesn't quite fit but I made it work.
I was all ready to return this because it did not fit my dual voltage travel dryer. Description states it will fit a 2.25in dryer, but the inside diameter of the diffuser is 2in, not taking into account the "teeth".  But I read on a different product review that if you remove the hard plastic vent, it is easier to stretch over your dryer nozzle.  Doing this, I was able to get my 2.25in diameter dryer onto the the diffuser!
Rating: 4 stars