New Canine Mouth Gag for Cat & Dog Veterinary VETERINARY MOUTH GAG SPRING ACTION Instruments Stainless steel Small, Medium, Large, X-Large, set of 4 pcs. The Canine Veterinary Mouth Gag is an instrument designed for oral examination and analysis of oral injuries that are relatively common in dogs and cats and include injuries to the mouth, gums, teeth, or tongue. Veterinary Practitioners and Technicians have trusted and used mouth gags in Cats and Dogs for years. Spring-loaded mouth gags have often been used to help hold the mouth open, allowing for procedures in the oral cavity.