Remove dirt from PCB or other sensitive components, and discharge static electricity to the ground. Brushes minimize static charge generation and dissipate ESD charge to ground when held by grounded personnel. Dissipative polypropylene black handled are able to remove charges to ground. Resistance of conductive fibers: 103-104 Ohms Resistance of dissipative handle: 105-108 Ohms Firm bristles are mainly for electronics, especially circuit boards. Very soft brushes can be used for optics etc.
