Ware Pet Products' Cardboard Critter Tube fulfills nesting instincts and provides a sense of safety and security while being completely safe to chew. It's an ideal crispy, crunchy chew toy for pet mice, rats, and hamsters. Gnawing on cardboard is irresistible to small pets and promotes clean and healthy teeth while helping overcome cage boredom. The hole down the center is perfectly sized to fit Ware Treat-K-Bob.