I wear this on my helmet and use it on flasher mode whenever I'm riding in traffic, day or night. The same light is available from at least two other distributors on Amazon under other brand names, including one for about $12 without the tail light included with the other two packages.

It's bright enough to be seen in daylight, but just barely adequate as a to-see light at night. I like it because it's so lightweight I don't even notice it on my helmet, and runs for many hours on flash. And it's very directional. Usually aim it slightly downward so it's not unnecessarily annoying, but by lifting my head slightly and looking directly at a driver I can tell the light gets their attention.

On the back of the helmet I've attached a Blackburn 2'Fer multi-mode light. Also very lightweight. I run it on red flashing mode in traffic, and switch to steady red when riding in groups, especially a monthly local nighttime group ride.

The head and tail lights both last about the same time per charge, assuming the same modes -- steady or flash -- and both recharge in the same time, so it's a convenient combination. The Blackburn 2'Fer has a built in battery gauge (the headlight does not), so when the Blackburn indicates it needs to be recharged, I plug both into the USB ports on my desktop PC. Depending on how often I ride I usually recharge them once or twice a week.

I'd guesstimate maybe one in 10 of the cyclists I see around town use lights in daytime. I see these more often on the local MUP, but rarely on public streets. By far most of the folks I see riding bikes in my area are impoverished or homeless, riding ill-fitting squeaky bikes, no lights or reflectors at night, often on the wrong side of the road.

But about once a week or so I'll see a serious cyclist kitted up in full regalia and running lights in daytime. Most of 'em use flashing mode, both the white front and red rear. Can't say it bothers me, although some folks complain. But so far most folks I've encountered are using fairly low powered lights, maybe 300 lumens or less, usually aimed slightly downward so they aren't blinding. I haven't encountered any cyclist running those overpowered aftermarket headlights so popular with young fellows in jacked up pickup trucks.