When you buy a dog life jacket, chances are you will have a size chart to pick on. You first need to know your dog’s size before you can get the right jacket. Since these sizes are made in specific measurements, it might be an issue to get a life jacket that fits them. The one thing you need to do when it comes to such a situation is getting them an adjustable life vest like the NAMSAN Dog’s reflective and inflatable life vest for swimming. Since it is adjustable, you can move around the straps to fit. When given a choice between a smaller or bigger size, the smaller size is recommended because it fits snugly on the dog. If you plan on getting it for a dog that grows fast, you might consider going the next size up, although you have to be careful with the straps, so it fits the dog properly.