The lever blade of some cross levers are shaped so that they are more ergonomic, so the top extends closer to the bar than the bottom. Other cross levers are symmetrical, like the ones operator showed. I'm using one of the asymmetrical levers on the wrong side on one bike, and while I can certainly feel the difference, it is not a problem for me, but if you have shorter fingers then it could be a problem because it requires very slightly more reach when upside down.