They are 6mm in diameter, which is the standard size for airsoft BBs.
Lancer Tactical Bio Tracer Airsoft BBs, 0.20g BBs have built-in tracer technology, allowing them to illuminate in low-light conditions when used with a compatible tracer unit. They have a smooth surface for improved flight stability and reduced jamming. The Lancer Tactical Biodegradable Tracer BBs are designed for use with tracer units to enhance your airsoft gameplay.