Ergo360 ESD Electrostatic Discharging Chair Caster Wheels Help Dissipate Static Charges That Can Damage Electronics (5 Piece Set) ESD (Electrostatic Discharging) Chair Caster Wheels are designed to help dissipate unwanted static electricity that can damage electronic equipment. They are a standard size that will fit many typical office chairs, stools, etc. Stem diameter is 7/16", please confirm this measurement before ordering. Wheel diameter is 2". This chair wheel has hard treads. Pricing is per complete set of 5 ESD casters. Specify a Qty of 1 for 1 set.. 2 for 2 sets.. etc. Please note, other components and proper flooring may be needed to provide a complete ESD solution.