American Mah Jongg consists of actually 152 tiles which is the largest number of all the variations. That is because the set contains 8 Joker tiles which act as wild tiles for the hands played. The White Dragon tile may appear as a blank white tile or in most cases a white tile with a blue border. It is often referred to as "Soap" and can also be used to represent a "zero" in those hands that require one.
American sets come with four or five racks, two or more dice, and some type of wind indicator. American players need a card. The Mational Mah Jongg League was founded in 1937 and produces the Official Standard Hands and Rules Card annually with changes in the hands that add more interest in the game. Some hands are kept and others are left off to appear another year. All American players use this same card. The proceeds from the sale of these cards and other products from the League are dontate dto charitable causes. Often these sets contain extra tiles (extra flowers, jokers, and/or blanks), and colored chips (circular chips with a square hole, reminiscent of old Chinese coins).
NOTE: If you buy an American set, you can use it to play Chinese mah-jongg or Japanese Mah Jongg as well (there are more than the required number of tiles present). But Chinese and Japanese sets cannot be used to play American mah-jongg (not enough tiles). So if you might want to use your set to play American mah-jongg some day, you should secure an American set and you can't go wrong.