i've tried these on a couple of bikes... not a massive, or even noticeable difference in power, but as has been stated, they do raise the redline limit, and have so far on my bikes proven to be a little more reliable than the standard "blackbox" CDI's fitted standard to nearly every pitty... and as gimmicky as it is, having the little red LED on them to show that yes, you have spark, can be a handy diagnostic tool when something goes wrong, as it gives an immediate indication that as far as spark goes, you should be ok...