I use Hardwood Stove Pellets from Lowes. Here is a link to the specific ones I use: https://www.lowes.com/pd/40-lb-Greene-Team-Platinum-Hardwood-Pellet-Fuel/50063465 Oddly, whenever I clean out my bun's litter box (every other day) it smells smoky, kind of like fire or a meat smoker. How weird is that? I was told these pellets are good for bunnies by a member on the forum but I'm getting a little nervous there's some chemical in it even though it says 100% natural. Anyone have experience with this smell? The actual pellets don't smell at all.