【Please refer to our size chart】: Back length 30cm, chest girth 54-64cm, life jacket weight about 0.174kg (Medium). Back length 40cm, chest girth 62-74cm, life jacket weight about 0.2kg (Large). Back length 45cm, chest girth 72-81cm, life jacket weight about 0.46kg (X-Large). Back length 50cm, chest girth 82-92cm, life jacket weight about 0.32kg (XX-Large). and there are buckles in both places. The buckle is adjustable, so you can easily help your dog put on the life jacket. After putting it on, you can tighten or loosen it according to the dog's needs. 【Unique Design】: The cute shark shape design with vivid shark fins and other details increases the fun of swimming and allows you to clearly see where the dog is when swimming. In addition, our safe swimming foam can help your dog swim without causing great fatigue. The top of the pet safety vest is designed with a handle that allows you to grab it with your hands or a boat hook, so that you can rescue the dog in case of danger. 【Easy