Royal Canin Vetinerary Feline Gastrointestinal HairballRoyal Canin Gastrointestinal Hairball Adult Dry Cat Food 2kg Complete feed for adult cats. Hairballs are a common digestive issue for cats and can often cause regurgitation, vomiting, constipation or slowing down of the transit. Hairballs tend to occur when hair that your cat has ingested while grooming hasn't progressed through their digestive tract properly. A diet that contains specific supportive nutrients can help with your cat's digestive issues