From the publisher's website: Add a little mayhem to your game. The Critical Fumble Deck is a sequel to our extremely popular Critical Hit Deck and is designed to balance out the system, allowing both minor and major mishaps to occur during combat. The Critical Fumble Deck consists of 52 full-color standard-sized cards, ready to use out of the box with the enclosed rules. The Critical Fumble Deck is compatible with the 3.5 edition of the world’s most popular roleplaying game. about the two versions Note to owners of the previous edition of this product: The only significant changes in the new Pathfinder RPG edition are that two cards now reference Pathfinder RPG page numbers instead of PH pages.