Logi cool Logitech MX ERGO Trackball Mouse This is a junk item. It can still be used, but the sensitivity of the left click has decreased, and sometimes it doesn't respond smoothly even when clicked. Therefore, it is listed as a junk item. Please purchase if you understand this and are able to repair it. In addition, the area where you rest your hand has become whitish due to use, and there is some deterioration. We would appreciate it if you could purchase only if you agree to the above.