The buttons holes can fit any 30mm buttons (sanwa or seimitsu snap-in), one start is 30mm and one is 24mm, the two yellow buttons are 24mm. As you can see you can make the panel for 8buttons each player (inside pic).
It fits a sanwa JLF w/o mounting plate, dunno about seimitsu.
It was for dreamcast and if you want i still have the vmu places.
Price: 30 + shipping (i’m from Italy)
(thread in other forums)