Well, technically-speaking, all
tia drivers need an acoustic chamber of some sort. Otherwise, there'd be no rhyme or reason to their tuning. The one on the customs are specifically called the
tia bore on their website, and it basically creates a controlled chamber so the
tia driver sounds the same no matter the shape of the custom. Since all the drivers in the universals are tubeless, they all require individual acoustic chambers, which makes things exponentially more complicated. But, yeah, it's just semantics at this point. 'Point is: They all sound at least pretty, darn good.