Enough room matters
The cat should fit without being compressed, while an oversized carrier can be harder to handle securely.
Door configuration
Top and front openings can affect how easily a cat enters and exits.
Cleaning
Removable liners and wipeable surfaces simplify accidents and routine care.
Travel rules differ
Airlines and other carriers set their own dimension and acceptance requirements.
General product-selection information only. A pet's health, anatomy, mobility, breathing and behaviour can change what equipment is appropriate. Follow product directions and ask a veterinarian or qualified animal-care professional when those issues matter.