Seriously? I had no idea, I think if I had one, I would use it every day, from what I have read it is fantastic, in fact, I'm even undecided between A18t and A18s. . . .
I use mostly full size headphones. A18t is good but I would be careful about auditioning the U18t and ordering the A18t based on that. My A18t has considerably less air in the treble than U18t, and this was why I ordered A18t rather than A12t. I have fit problems with most IEMs, so wanted a custom. But if I knew that outcome, I would have rather gone for A12t or even U18t.