These are the Lenovo 4Y50R20863 (with the red mouse wheel, not the cheaper GX30M39704 with the orange mouse wheel), and they're VERY well made. The Lenovo website currently lists them for $16.99 apiece and I got three of them (brand new) for that price. I always pick up extras when I buy replacement mice because I'm pretty hard on mine and these are rated at 8 million clicks, so I couldn't be happier! =D

This mouse (part 4Y50R20863) is fine for typical office work (spreadsheets, word processing, etc...), but probably not the best for playing games. The buttons are not separate from the body, so the clicking motion can be a little bit on the stiffer side. The shape is okay in that the "hump" is closer toward the end / bottom of the mouse rather than the middle (still comfortable). Very affordable. The weight seems to be good too - not too light nor too heavy. This mouse is identical to the one which came with my Lenovo ThinkStation. There is another USB wired Lenovo retail mouse (part GX30M39704) which looks the same as this one, but that retail one has an orange wheel, where as this one has a red wheel.

The essential mouse works well except the feel is not comfortable due to the texture of the plastic. It causes the fingers to slide off. Also, when recording videos, you can hear the clicking of the mouse. A softer click is needed.