The opening where it attaches to the dryer is expandable with an elastic band inside like many other diffusers have. It may not stay on a tapered nozzle that is narrower at the bottom and gets wider as it goes up. I don't think I've ever seen a square nozzle, but as long as it'll fit into the round opening (I'd estimate it's 2.5-3" across), the way it adjusts, it could conceivably stay on.
Got mine at Ulta but I had to ask about it - it wasn't with the other diffusers or with the other Deva products. $39.99 unless you have an Ulta coupon of some kind. This includes the hand-shaped diffuser, the adapter attachment, and a travel-size bottle of Set It Free.