See pics for proof of him signing. The product is an autographed hat cap by Isaiah Hartenstein of the Oklahoma City Thunder. It is an original item signed by Hartenstein and comes from a specific event or tournament where the Thunder played against the Phoenix Suns. The hat is made by New Era and is a 9Fifty style. The autograph has not been authenticated. Overall, this is a unique and collectible piece for fans of Isaiah Hartenstein and the Oklahoma City Thunder.