Mah Jongg tiles have traditionally been made of bone, often with a bamboo backing. Bone tiles can still be found but most modern tiles are constructed using plastics. A small number of sets have been made with jade or ivory, and these sets are rare.
Regardless of what a tile is constructed of, the symbols on them are usually engraved or etched into the tile. Some experienced players can determine the value of a tile without looking at it, by feeling these engravings with their fingers.
There are two main categories of sizes for Mah Jongg Tiles, a larger size range used in China, and a smaller size range used in the US and most of the rest of the world.
The Chinese size is further sub-divided into 4 generally used size ranges which are:
8 ~ 39 × 30 × 23 mm
7.5 ~ 38 × 28 × 22 mm
7 ~ 36 × 26 × 21 mm
6 ~ 34 × 25 × 19 mm
The ratio of length to thickness in the Chinese sizes is usually over 1 to 1.5, so that the tiles can stand upright, since Chinese players typically do not use racks to support their tiles.
The sizes typically used in the US and the rest of the world (other than China) have lengths that vary roughly between 3 cm (1-5/32″) and 2.5 cm (1″).
The Japanese typically use tiles thicker than those used in the US, so they can stand upright without a rack, as the Japanese players like the Chinese, normally do not use a rack
Racks are commonly used along with slimmer tiles by players in the US.