Birds are incredibly smart, and a challenge toy can provide hours of stimulation. In nature, foraging for food and treats are part of daily life. Can-O-Nuts™ is an incredibly strong plastic container. It is actually made from materials used to manufacture bullet proof glass. That is why we say it is Bird Proof™! Simply stuff with nuts or other favorite treats to keep your pet challenged and stimulated. The small is 3.5 inches tall and 2.25 inches wide. The large is an impressive 4.75 inches tall and 3 inches across.