I buy 40 lb bags of pine pellets at tractor supply but any feed store should have them. They sell it as horse bedding. You can also get big bags of pine shavings for about $6 depending on your area. Aspen shavings for a big bag runs about 10 bucks at tractor supply but I only use aspen for the rats. The chins and bunny get the pellets, it doesn't kick out as easy and vacuums up nicely.