This page showcases the pips that can be used with the Settlers of Catan board game.

Click on any picture for a larger version

The pips are all made of birch.
Each pip has a large number signifying the dice roll surrounded like a dark, recessed ring.
Inside the ring is a representation of all the possible dice rolls that can cause the number to result.
The relative probability can quickly and intuitively be understood by comparing how many possible dice rolls one number has versus another.
The 3 shows 2 dice rolls, and the 5 shows 4 dice rolls, so it is twice as likely to roll a 5.
The pips are designed to fit together with the Robber so that the robber rests perfectly on top and won't slide around.

Please see my blog, Boardcrafting for more background information.