These are

dice which can be used anywhere a normal

six-sided die is required. Each die is a

sphere with the numbers 1 to 6 printed evenly on the surface. Inside, the

die is

hollow and contains a small

ball bearing which falls into one of six pits. These pits are aligned with the numbers on the surface, so the weight of the ball bearing will cause one number to remain facing upwards.

Of course, the idea isn't limited to only six-sided dice. However, adding more "sides" makes

construction of such a die much more

complex.

Spherical dice have no particular

advantage over regular dice, and take forever to stop

wobbling.