• Brushes minimize static charge generation and dissipate ESD charges to ground when held by grounded personnel
• Dissipative polypropylene black handles are able to remove charges to ground
• Resistance of conductive fibers: 10E3 - 10E4 ohms
• Resistance of dissipative handle: 10E5 - 10E8 ohms
• Firm bristles are mainly for electronics, especially circuit boards
• Bristles are a mix of conductive synthetic yarn and horse hair 

ESD Handbook TR20.20 Table 1 lists under Typical Static Electricity Sources "Brushes (camel/pig hair and synthetic bristles)." "It should be understood that any object, item, material or person could be a source of static electricity in the work environment. Removal of unnecessary nonconductors, replacing nonconductive materials with dissipative or conductive materials and grounding all conductors are the principle methods of controlling static electricity in the workplace, regardless of the activity." (TR 20.20 section 2.4)