We HIGHLY recommend that you measure your pet before placing an order. Your pet can be a medium in one product and be a large in a different product. Our size guides should help you figure out what size you should order for your pet in a specific product. Each product has a different size guide! Refer to the size guide of the product that you would like to order. If you have any trouble figuring out your pet's size in a product, feel free to reach out to us via email at mejoramigopetsupply@gmail.com or for a quicker response use the chat feature on the bottom right corner of our website and ask us on there. We're always happy to help.