I'm running an internal rotor on my maxi and using this as the tail light. Pretty bright, bolts right onto maxi fender once u remove the old light housing. Nice over molded rubber button and gaskets in it to keep water out. You need to remove two small allen bolts to change the batteries, but because it's just one LED bulb, the AAAs last long.
The little metal guard broke off on mine from vibration. It would be useless if it actually hit something. Oh well, i didn't buy it for the guard, it looked kinda weird anyways.
If the light flickers when riding, fix it by putting a little piece of tape on the batteries to keep them from vibrating/spinning.
simple solution 
