The product is a rare vintage Japanese Pokémon TCG card featuring a Mewtwo with a dark Slowking on its back, making it a unique error version. This collectible card is made of card stock and has been professionally authenticated by PSA, adding to its value and authenticity. With its green attribute, basic stage, and misprint features, this Mewtwo card is a sought-after item for collectors and fans of the Pokémon franchise.