Check movement
Shoulders and legs need normal movement.
Look at closure placement
Closures should be secure without creating pressure or rubbing.
Think about drying
Water-resistant outer fabrics are more useful when the garment also dries reasonably between walks.
Visibility can help
Reflective trim can make a dog easier to notice in dark, wet conditions.
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.