The Glass Z-core is indeed 19/22 and has been reported to fit RBT devices no problem
. The next drop of wood kits (sleeve + mouthpiece) is scheduled for this coming Sunday at Noon eastern time.
The glass by itself isn’t that special, like
@StringTheorista said, aside from being American glass fabricated by a scientific glass company. They made the casting molds to my specs, so it’s really high quality and a great fit with both the basket screen and the ground joint. Basket sits nice and flush, doesn’t stick out like on some other joints.