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From personal experiences, I know that this type of cage is definetly pet friendly. This is the perfect home for small animals. Toys and beds easily attatch, and provide small excersize pieces. The only concern, is if plastic is harmful to your animal, which is the composition of this cage.
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This small metal cage is a great example of what to look for when shopping. One major detail that should be noticed is the length between each metal rod. In order for these cages to be safe for small animals, there needs to be at most 1 inch between each bar. In addition, small accessories fit perfectly in this small animal cage.