Alfie Couture Designer Pet Apparel - Jon Racing Jacket - Color: Red, Size: M Please note that this listing is for size Medium. Best fit Neck Girth: 10.5", Breast Girth: 15.5", and Body Length: 11.25". We recommend one size up for comfort if your dog's measurement is the higher end of the range listed. Please note that these lengths represent the size of the dog and do not reflect the actual length of the garment. Sizing for each dog is unique. Similar to our clothing and accessory, medium size from one designer is not the same for another. For example our 9-pound yorkie model usually fits either one of three sizes (i.e. XS, S, M) depending on the designer. We highly recommend you measure your pet precisely with a flexible tape measure to ensure the best fit. Contact us if you have question. We are happy to help.