Is that the new one which doesn't work as butane vape?
Yeah you'll be fine, all of the cooling stems will fit a Z, only the earliest US ones were not 19/19, but they were still Z sized. And any custom one can work as a vape, with the glass thick enough, the standard Chinese ones may be too thin to try though. You also may not want to use one you use as a stem as a vape, I think it affects it a bit... Haven't tried myself.
Yeah, and I have a couple stems that are a little wobbly but not too long and do fit, they are airtight, but there is just a lot of variance with glass. as I've mentioned before, maybe it was in this thread or the main splinter one, but I posted that photo of a bunch of different 18.8mm stem joints together, which all fit my custom Z and Milaana II (but not my standard V2)