1/8 Galvanized Hardware Cloth is also available, which I would be more secure using, just to be thorough. I disagree with one comment suggesting that they can expand the material and get through - not so if it's galvanized or stainless steel, which it must be. You cannot use softer metals such as aluminum.
Here is a very comprehensive and informative document on proofing from those critters:
http://icwdm.org/handbook/rodents/rodentexclusion.asp
All the best & Good luck!