Size M (Cir: 8.75-9.5, length: 2.253) Size L (Cir: 9.75-11, length: 2.53.25) This dog muzzle medium sized dogs fits Border Collie, Beagle, Corgi, etc., but not for aggressive dogs, highly anxious dogs, and flat-faced dogs like Bulldogs. Measure your dog's snout circumference and length per the size chart or video. Ensure the muzzle fits comfortably, with the nose not touching the edgePatiently Muzzle Training to Reduce Escape & Resistance-As a training tool, it's normal that your dog may feel resistant and take this mesh dog muzzle off quickly at first serval times. Your dog will gradually adjust with consistent positive reinforcement (treats and praise). Reduce Odor by Airing Out and Washing-Due to prolonged sealed shipping, the muzzle may have a slight odor. Please place the dog mouth cover in a cool, well-ventilated area for a few days, or wash it with a mild detergent and air dry. Rest assured, our muzzles are non-toxic and safe, posing no harm to your dogs healthCorrect Bad Habits with Muzzle Training-Designed with an innovative semi-enclosed design, this muzzle for dogs effectively blocks your dogs mouth to prevent biting, eating branches, and chewing furniture. Please note, the muzzle is a tool that provides restraint but won't eliminate bad habits. Changing your dog's bad behavior requires patience, guidance, and trainingMaximum Ventilation and Comfort-This soft dog muzzle features a breathable mesh and open-front design, allowing your dog to pant and cool down easily. This soft muzzle for large sized dog reduces the risk of overheating and nose irritation, ensuring maximum comfort during active playEasy to Use-Equipped with an adjustable neck strap and quick-release buckle, this Labrador muzzle can be put on in just 30 seconds. The easy-to-use buckle makes it simple to put on and take off, ensuring a joyful experience for you and your dogCustomizable Fit-This no bite muzzle for dogs allows for easy and precise fitting with a wide adjustment range at the top of the nose. You can effortlessly adjust the tightness to suit the shape of your dog's nose, ensuring a snug and comfortable fit.