The cards are multiple sizes.
Guests are 6cm x 9cm
Room upgrades (extra beds, phones, etc.) are 2.25cm x 3cm
Action cards, staff cards, and hotel upgrades are 4.5cm x 6cm
Thank you very much for the information. I found sleeves that should work well for the Guest cards, and for the action/staff/hotel upgrade cards. I don't know of any sleeves small enough for the room upgrade cards, but I'll keep looking.