The listing, Newish 24" X 36" Grounded Antistatic Floor Mat for Working on Electronics-Free US Shipping has ended.
I believe this is an older model of this mat - http://www.crown-mats.com/products/statcontrol.html. It retails for about $65. I bought it but never used it. You can use it while seated on a chair on top of it for working on sensitive electronics. It comes with a grounding wire you can insert in the third wire hole of your electrical socket.
I never used it because I became less concerned about static damage to my computer parts after the scare we were put through during my initial training.
The mat has a heavy foam backing and a spongy underside. It's glossy black on the side facing up. It will come with the wire. The corners though are rounded which might mean it's a different company and model than the one described below:
"• Medium-Duty, Dry Areas
• Computer Work Stations
• Work Stations
• Cashier’s Station
• Test Stations
• Electronic Stations
• Service Counters
BENEFITS
• Static dissipative
• Stock mats include grounding cord
• Resistivity is 107 ohms per square
• Beveled edges and easy-to-clean surface
PROPERTIES
- Thickness: 3/8”
- Material: Vinyl top with PVC foam backing
- Anti-Fatigue
AVAILABLE IN
- Colors: Black"