The size and shape of different mice may change but the fundamentals usually remain the same.

The Roller Mouse Free is different. It sits below the keyboard and has a rolling bar at the top to control the pointer.

The bar rolls back and forth but has an attached pad that can be moved from side to side. Between the two, you can move the pointer in any direction.

This minimises hand and wrist movement, which, along with the large wrist-rest pads on either side, certainly made for more comfortable working.

There are buttons for left and right-clicking, a scroll wheel for moving inside a document, special dedicated buttons for copying and pasting and a double-click button. The latter three were handy but it took us weeks to get used to them.

Although the Roller Mouse Free is designed to sit below the keyboard, we found that we could not use it there and type without accidentally moving the mouse pointer. We ended up moving it to one side, which negated its point a little.

It is also extremely expensive compared to regular mice but for RSI sufferers that might be a price worth paying.