Ball Bearings (more commonly known as BB's) are a generally small and circular piece of itinerary used in varying machining and mechanical designs from scooters to train wheels.

In hobby culture, they are widely used as munitions for air guns and come in plastic, copper, steel and even aluminium and glass assortments.

Table of BB Materials and Power
Material Speed Penetration Cost
Metal Low-Medium High High
Plastic High Low Low
Glass High Low-Medium Low-Medium
Magnetic Medium Low-Medium High
Lead Low Very-High High