This class includes games which do not use the standard poker hand rankings to determine a winner.
Aces are low.
Instead of 3 chips which are lost one at a time, losers pay a higher amount and are knocked out immediately. This yields a faster game.
When down to two players, the last player has an advantage-- if the first player exchanges with him, he knows what all the cards in the game are and can make a more informed decision. To cancel this advantage, when only two players are left the second player can't look at his card until after the first player has chosen to exchange or hold.