Some modeling tasks require quality brushes. Application of the base coat, painting of fine details, or figure painting for instance. And it's important to keep them in good condition.
Some other tasks, however:
Don't call for the use of expensive brushes, because precision is not important.
Can be very aggressive to our quality brushes and destroy them over time, which is a waste of money.
Think mixing paints in the airbrush cap, applying and blending weathering products, dry brushing over a rough surface...
For those cases, even synthetic brushes can be overkill, and disposable brushes are the best option.
These sets of brushes include 50 pieces of small size brushes. They can be used once, and discarded immediately, knowing each individual brush only costs a few cents.
We have to prepare each shipment individually as they are ordered, so allow it in 3-4 weeks to arrive in the USA/Canada (to be safe) and 3-6 weeks rest of the world, though they are usually delivered much faster.