I remember. A part of the top shell could snap off and be replaced with a third-party shell that gave the mouse a more elongated shape. There were at least two

I remember. A part of the top shell could snap off and be replaced with a third-party shell that gave the mouse a more elongated shape. There were at least two such shells on the market, even. While you could use any other USB mouse with Mac, MacOS had a mouse acceleration curve that felt odd. One thing special with the Microsoft optical mice is that they came with a driver for MacOS — with its own mouse acceleration code that fixed this issue.