As per title, what do I search for so I can buy some. I use it to clean dust off circuit boards.

20mm wide to give you an idea of scale

Expression Synthetic Precision Brush?

[Edited on 21/9/17 by number-1]

Suds Brush?

See: http://www.hgrant-brushmakers.co.uk/category/3/cleaning

Mother in law used to drive one like that.lol

I used to swipe the wifes make up brushes to clean the insides of computers.

Don't use synthetic. Static !

Could it be a fitch brush , looks like a worn one.

if you want to cover the cost of postage i will send you a few