Woofie's is strictly a retailer of pet products; therefore we resell products from many different vendors. All of our collars, harnesses and pet apparel contain specific information about their sizing. Many manufacturers vary in their sizing, so it is important that you read the sizing guidelines for each product, measure your pet carefully and order accordingly for each product. If you have any questions, we encourage you to contact Woofie's either by phone or email. We will help you properly measure your pet so you can complete your order accurately.