Aoqun website has a complete set of volumetric flask cleaning brushes.

They have small volumetric flask cleaning brush has a diameter of 20mm, a filament length of 65mm, a total length of 180mm, a nylon filament, a head fan shape, and a 10mm loop at the end. The small volumetric flask cleaning brushes can be ordered separately and will not be bundled, as the brushes are custom made to match the brush to each product that needs to be cleaned.

If the size of this small volumetric flask cleaning brush is not suitable, Aoqun can also make adjustments based on the information provided by the customer.