Bio-Rubber Mat by Yamamoto Chemical Industry. This item was sold with a triangular cut. It's easy to use and portable, you can place it on your stomach or sit on it. ⭐︎With cover There are dents on the surface of the Bio-Rubber Mat. Mat thickness: approximately 9mm, 14cm square Retail price: around 30,000 yen This is a used item and has been stored at home, so please refrain from purchasing if you are concerned about minor imperfections. Thank you for your understanding.