The BBs have a diameter of 5.95mm with a deviation of +/- 0.01mm. In addition, the surface is made very evenly. Thanks to a special coating, the hop up rubber grips the BBs a little better. The Bio BB series also has the advantage that the BBs decompose independently through heat, moisture and pressure in nature and thus protect the environment. The BBs can be stored very well here in the 4000 resealable bag