Fiskars is also a material that will dull blades, unfortunately.
The better mat is from Olfa, the first and original mat for quilters. It was designed for the engineering industry and is truly "self-healing. You can get them for a decent price at Hancocks of Paducah as well as Joannes.
http://www.hancocks-paducah.com/NOTIONS/Cutting-Mats
Jan in VA