ROCKBROS Bike Tail Light Smart,Brake Sensing Bicycle Rear Lights,Ultra Bright LED Back Lights,Type C USB Rechargeable,IPX6 Waterproof,Cycling Safety Taillight Accessories

I purchased this taillight to augment the anemic flasher on my Garmin Varia Radar. The RockBros light is a great value and an excellent rear light. A full charge seems to last forever and the brake light function is appreciated by riding partners. The light is very bright and easily visible even on a sunny day. The light came with two mounts, a strap for the seat post or a clamp on mount for the seat rails. The light screws into either of them just like a bottle cap. The charging port is accessed when you unscrew the light from the mount. The strap mount works fine, but as a rule I just don't trust straps. I used the clamp mount, which installed easily and holds the light in place on the rails. The clamp was a slight bit loose on my rails, but a small bit of tape under the clamp fixed the issue. I've used the light for about 1500 miles on gravel and trails with no issues. Taillights are a simple bit of kit, but I really appreciate the added visibility, both day and night. Hard to beat the value and function with this light.

UPDATE: Rockbros refunded my purchase price, and I will re-buy when they make a unit that has auto on/off and motion sensing in the daylight. Outside of that, it is a very nice unit. Small and bright, with a good mounting system. The brake light algorithm seems to work well. UPDATE: The Q5 is a Tail light. The one I have, does not have auto on/off, motion sensing in the daylight - despite what RockBros.says. In fact, if you very carefully read the PR info, it says this. The tail light has manual mode, strobe flash and contiguous in the daylight, not auto on/off motion sensing. The RockBros Q5 tail light Has several problems. There is no way to shut off the ambient light sensor for the blink and breath functions. This makes it useless in the daylight and only useful at night. So the kid riding to and from school does not have a tail light, which is why I bought a vibration sensing/auto shutoff light in the first place. The manual says that mode 3 and 4 (strobe blink and continuous) are useful in the daylight, but they do not have vibration sensing or auto shutoff. So to get into that mode you have to push the button through all the other modes, and same to shut it off - not very "smart". So, I took the unit apart (thus voiding the warranty) to see if I could cover up the ambient light sensor. That didn't work because they use the off cycle of all the LEDs to sense ambient light. So, I had to block all the LEDs to keep it blinking in the daylight. I asked this question before I bought it, and got an inexact answer back from someone who is not a native English speaker.

Excellent tail light! Super bright, automatically senses braking, and adds great visibility at night. Easy to mount, long battery life, and very reliable for safe rides.

Good build quality and mounting hardware feels secure. I like the two mounts included; one light for two bikes; just unscrews from one mount to screw onto the other. USB-C charging is always nice. The 4 modes have good options for always flashing or motion detection. Brightness is pretty good for night-time, but won't overcome sunset-type conditions and the light is not very noticeable in daylight. I'd recommend finding a brighter rear light for day time. The 4 dots for battery level are helpful but don't work great. I haven't seen 1 dot "25% battery life" because it dies after it gets to 2 dots. That said, if it's charged up the battery life is still decent and overall still a good light.

It just works. The accelerometer braking feature is really nice and the motion sensing to save battery is perfect. Thread in mount protects the USB port, perfectly. What a great design. Long life. Bright. Useful modes.