I remember seeing this card on websites before, but never purchased it.
The biggest card I ever had was the "Massive memory card plus" which had 8 Banks of memory. https://segaretro.org/Massive_Memory_Card_Plus
Though don't ever use that with PSO saves, its prone to corrupt on those. I lost a lot of challenge mode characters on that thing. Ended up just using it for PSO screenshots and 4X4 Evo download tracks back in the day.