Recently had the urge to play some retro, and realized I needed some memory card(s). I purchased a used pkg that included some memory cards but ended up being for PS2. I couldn't remember if they were interchangeable so went to insert one into the PS1 and it won't even fit. I was sure that the cards were physically the same parameters, but all three will not go in even a little. I now know that to actually use it won't work, but I'm puzzled why they won't fit into the slot. I pushed the doors open and all looks normal from what I can tell. Maybe I'm missing something. Thank you.