AS others have said, check with the shelters. They have specific requirements to fit the cages and also their capability to wash and clean the mats. Our guild donates them and mats are wanted for dogs and a hammock style for cats. As for stuffing, I use old towels batting remnants, etc. If you tell people what you're doing, and ask for any clean, old bath towels, you'll be surprised by the response. Better than being sent to a landfill. Enjoy the process.