This may be of interest for those looking at TWSBI alternatives. I've had great luck with TWSBI (no cracks yet) and so-so luck with WingSung (one cracked badly). Others have had the opposite experience.
From top to bottom: WingSung 3008 (~$3.75 USD), TWSBI ECO (~$35 USD), WingSung 698 (~$25), TWSBI Diamond 580 ALR (~$65). All are piston fillers, all seal really well. 3008 feels flimsy but works OK. Others all feel solid. No stub nibs on WS, though.

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