The housing line on a switch spec sheet is the second-most-important thing about a switch, after the type, and most buyers skim past it. Material decides how the switch rings, how the stem rails feel under a finger, and how much grace it gives a bad lube job. A 'PC top, nylon bottom' tag is doing more work than its three words suggest.
Gazzew designs, Outemu molds, and a plastic softer than nylon does the rest. Every Boba is the same chamber with something deliberately left out — and the pattern of subtractions is the whole family tree.
The Durock T1 keeps turning up as the comparison point in other switches' deep-dives — the reference a reviewer reaches for when a bump needs to read as heavy and serious. It has never had its own.
Same housing, same bump position — the U4T's whole personality comes down to what Gazzew left out. Pull the dampening pads from a Boba U4 and the bottom-out stops being polite.