Thank you for viewing. This is a listing for the Logitech silent wireless trackball mouse MX ERGO S (Bluetooth compatible). It was used for less than 6 months, and I believe it is in good condition. The reason for the "defective" status is that there is a problem with the right-click function. Although the right-click itself works, it requires a slightly stronger press compared to the left-click to register, which is why it is listed as defective. All other functions work without issue. I hope that those who do not mind having to press the right-click a little harder, or who are able to repair it themselves, will consider purchasing. Thank you.