Yesterday's News is also a good substrate =) Theres a link on here somewhere to a page hosted by a woman who claims to have found sharp items in her bags of YN and also claims Purina told her they use saw house floor sweepings in the product. However, I phoned the company and they assure me that that information is 100% untrue, and I have also never found anything sharp in the litter in 15 years of use for various critters. I did however find a piece of broken grinder blade in woodchips once.. but only once =) I WAS using eco-earth but find its too expensive for me, where as 20kg of YN is $8.00 (here 5kg of eco-earth is $32.50).. and I have no access to aspen ~,~