This is a current model from Logitech. It uses the "Flow function." Please check the following site for details. Size is S/M. Graphite Signature Plus M750: M750MGR https://www.logicool.co.jp/ja-jp/shop/p/m750-signature-wireless-mouse.910-006920 [Notice] * Purchased from the Logitech shop in November 2025. * Used for about two weeks, but selling because the size doesn't fit. Therefore, as shown in the photos, there is some wear and tear. * "2-year free warranty" is included. There is also an uncompleted warranty card, but in my experience, Logitech should be able to handle it if you contact them and provide the serial number inside the battery compartment. * If you want, I can include the batteries that came with it. I cannot guarantee the remaining battery life. Thank you for looking.