I bought this diffuser attachment at my local Sally's because the flat type diffuser that come with my hair dryer gave me weird wonky waves. I love this thing sooo much it's almost ridiculous. It gives me consistent ringlets because the hair just lays better in the deep bowl vs the flat diffuser. I have never had a problem with it fitting on my Revlon Ionic Pro Stylist 1875-Watt Dryer. I have had for almost 2 years and it still fits perfectly.
I have had this attachment for almost 5 years. It's great! The red thing fell out about 2 years ago, but it works the same as ever, in fact I like it better without it. Much better-formed (S-shaped or round, not weirdly angular) curls and waves with this diffuser than the other 2 attachments I've tried.