ESD (Electrostatic Discharging) Chair Wheels are designed to help prevent unwanted static electricity that can damage electronic equipment. They are a standard size that will fit many typical office chairs, stools, etc. Stem length is 7/8". Stem width is 7/16". Wheel diameter is 2". This chair wheel has hard treads. Pricing is per complete set of 5 chair wheels. 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. Satisfaction guarantee, if chair casters do not meet your needs, just return within 30 days for a refund. Shipping is not refundable. If you have any questions, just call toll free.