buy one from a local retailer so you can try it out. otherwise be prepared to buy one test it then buy more, or if you prefer a different one then keep the first as a back up. I only carry spare on long rides when my trip home might be a long time away from my trip out. 1 PBSF on back rack and left drop bar, w one magic shine up front. I started with the PB 1 watt headlight - which is ok for a be seen strobe in shade and elsewhere too, but magicshine is much brighter. it's inadequate as a headlight to see at night. I think even the 2 watt would barely be good enough considering the much better option such as magic shine and it's cheap copy. I have the cheap copy too but haven't used it yet cuz I just pleasure bike now and my new magicshine battery needs use.