A: There are three different decks in Pyramid Arcade, each a very different size.
The Zark City deck is like a regular deck of playing cards, except that it has five suits and the cards are square. Measurement (roughly, using a ruler) is: 2 & 5/8″ (7 cm) on a side.
The Pyramid Arcade deck, which has a card for each game in the set, has more familiar dimensions. I believe they would be called “poker sized” (wider than “bridge sized”). These are 3 & 7/16″ (8.75 cm) tall by 2 & 15/32″ (8.8 cm) wide.
The Twin Win deck has miniature-sized playing cards which measure 2 & 11/32” (6 cm) tall by 1 & 9/16 (3.95 cm) wide.