Penn Plax Gravel Paper for Bird Cage, 9 by 12-Inch The gravel helps to keep the beak and claws of birds trimmed. Gravel sheets provide grit for hard- billed birds and aids in digestion. Gravel paper is also safe, clean, and sanitary to keep your pet happy and healthy. The gravel helps to keep the beak and claws of birds trimmed Gravel sheets provide grit for hard-billed birds and aids in digestion Gravel paper is also safe, clean and sanitary to keep your pet happy and healthy