Simplify the following text for a Grade 6 native English-speaking person.
Original: Dice for role-playing games are usually made of plastic , though infrequently metal , wood , and semi-precious stone dice can be found . Early polyhedral dice from the 1970s and 1980s were made of a soft plastic that would easily wear as the die was used .
Simplified: Dice with different numbers of sides are called polyhedral dice .