These thumb shifters are unusual because they fit on both road and MTB sized bars. Therefore, they fit on all handlebars. They even work on drop bars, but not on the sleeve.

They are not Campagnolo quality (what do you expect for $16 per pair) but they do function perfectly, and the soft rubber tipped levers are actually very comfortable. 

Installation is very simple-undo the bolt from the bracket it is threaded into, bend the bracket to make it curve around the bar, slide it on the bar, clamp it a bit tighter and then install the bolt through the hole in the top of the bracket into the threaded portion below. Tighten it up and you're set.

Cables are included. Price is per pair, a left and a right.