Dungeons And Dragons RPG Game Master's Toolbox: Critical Fail Deck - Rules of Play says:
Is your d20 failing to give you anything other than 1’s? Well, make things more interesting with this deck of critical failure outcomes! This deck contains all sorts of consequences to the dreaded critical fail, from the dangerous to the downright embarrassing! Each Critical Fail Deck will include:
52 cards for use by both the players and the GM
4 different outcomes per card depending on attack type: melee, ranged, natural, or magic
208 amusing, dangerous, or embarrassing critical fail outcomes!
Dungeons And Dragons RPG Game Master's Toolbox: Critical Fail Deck Video:
Don't just take our word for it! Check out this video showing the Critical Hit Decks!