I use it in the mezzanine level of my C&C only. That's because it's a "forage tray" for the pigs, so it's nothing but hay and sometimes bits of dandelion, herbs, berries etc. mixed in for them to sniff out. I wouldn't use it in my whole cage as it simply isn't absorbent enough. When mine wee on the upstairs level it goes straight through 3-4 layers of newspaper no problem. Also, if you can't change every day or two, hay can get musty pretty quickly, which doesn't smell nice and may be bad for their breathing.