The Flash rear LED from Edinburgh Bicycle Cooperative's Revolution range is a pretty good option and a bargain at under a tenner. It's integral mounting system means it's very quick and easy to put on or take off your seatpost. It charges via a USB cable and, as long as you remember to charge it, battery life won't be a problem.
The best thing about this light is the mounting system. The whole light is encased in a silicone moulding; this includes a strap that you put around your seat post and hook back onto the light. Very easy, very simple, very quick; no tools required. Good news, as long as your seatpost is where you want to put your rear light. If you have a saddle bag taking up that space, for example, you're out of luck.
Although the Revolution Flash does a good job, it's not up there with the brightest rear lights. It uses a single LED and makes the most of it with a clever lens, pointing all that red goodness right behind you - but hardly any to the sides. I think it's best used as a back-up or secondary light to a brighter main light. At only 36g on the Road.cc scales, it is ideally suited to this job.
Charging takes under 2.5 hours and is done via a USB cable that plugs into the back of the light. Revolution don't claim this design is waterproof. Although I've not had any problems riding in the rain, I would be careful in the wet if you don't run mudguards or if you're planning to take it off-road.
The USB cable is the same as you get with many other electronic devices, so you might well own a spare cable already. According to Revolution, the light is good for 500 charge cycles.
In use, the light has two settings: constant and flashing. The runtime on flashing is up to 11 hours. On constant I found it to be nearer 3-4 hours.
It works well as a secondary light, but not enough visibility to be a main light.
road.cc test report
Make and model: Revolution Flash Silicone Rear LED Light
Size tested: Red
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
They say: "Fantastic value USB-rechargeable LED rear light". I'd go along with that.
Tell us some more about the technical aspects of the product?
The single high-lumen LED and its magnifier lens are encased in a robust water-resistant, silicon-rubber lamp body.
2 operation modes: constant beam or flashing.
Integrated design: a stretch silicon strap is part of the lamp's body.
Supplied with a simple USB charger LED.
The lamp's indicator light changes from red to green to inform you when the battery is fully charged.
Charging takes no more than 2.5 hours.
Life expectancy: 500 charges.
Run time: up to 11 hours.
It is well-made and has stood up to well to some bad weather.
Although the LED itself isn't that high-powered, the lens does a good job of throwing all the LED has got to give at anything behind you, which is plenty for a back-up light, but I'd go for something stronger for a ride in the proper dark. There is no side visibility to speak of.
Revolution reckon 500 charge cycles. That's not bad for under a tenner.
It's really easy to put on - and take off - your seatpost.
Less than a tenner...
Tell us how the product performed overall when used for its designed purpose
As a second light, it's pretty good. However, I'd only use it as a second light, or as a back-up to something stronger. It's not really got enough punch to be your main rear illumination, and there's also a lack of side visibility.
Tell us what you particularly liked about the product
It's so easy to swap between bikes.
Tell us what you particularly disliked about the product
The battery doesn't last that long – around 3-4 hours on full.
Did you enjoy using the product? As a second light, yes.
Would you consider buying the product? Probably not.
Would you recommend the product to a friend? If they were looking for something easy to put and take off their bike, yes.
About the tester
I usually ride: All of them! My best bike is: Cervelo Dual
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, commuting, touring, club rides, fixed/singlespeed, Audax