Splitting the difference between the previous Flux 800 and 900, the Flux 850 gets the game-changing Mode Shift found on the Flux 1250. This means there are three steady modes, all using both the wide and spot beams. Go from Steady Low to Steady High in a single push, without cycling through a flash mode. Press-and-hold for two seconds and you get into the secondary modes: Steady Flash to be seen in busy urban environments, Flash Mode for endless runtime, and two Flashlight modes with 10 and 20 hours of runtime for hanging around the campsite, or when you forget to charge your light and need to conserve the last few percent of battery life to get home.
IPX7 waterproof means this light can survive being submerged 1 meter deep for 30 minutes. No, it's not meant for scuba diving. But is can handle anything you can throw at it on two wheels.