The BBs have a diameter of 5.95mm with a tolerance of +/- 0.01mm. Furthermore, the surface is very evenly manufactured. A special coating allows the hop-up rubber to grip the BBs slightly better. The Bio BB series also has the advantage that the BBs decompose naturally through heat, moisture, and pressure, thus protecting the environment. The BBs can be easily stored in this 5kg bulk pack with a resealable bag.