Thundershirt.com provides a satisfaction guarantee on their products, which is designed to ensure that customers feel secure in their purchase. If a customer finds that the Thundershirt is not effective for their pet, they may be able to return the product for a full refund within a certain time frame, typically thirty days from the date of purchase. This policy is meant to give pet owners the confidence to try the Thundershirt with their animals. However, any specific terms and conditions regarding the guarantee or warranty can vary, so it is advisable for customers to check the current information available on the Thundershirt.com website. This will provide the most accurate and up-to-date details regarding return policies, as well as any warranty information that may apply to individual products.