I'm currently using 2 Cateye TL-LD610's which claim to have 80,000 candlepower each. My drives are in 20, 30 and 50km/h zones so they're definately good enough. The second is really only for redundancy in case one decides to die or the batteries go south. Chances are it won't happen to both at the same time and I want at least one working. The units are reasonably water resistant and I added some Vasaline to the battery access door to help out. Run time is good enough that I can just recharge the AAA batteries once a week while using them every day.