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For such a small lumen count, the Lezyne Femto Duo is quite a punchy light for sitting atop your helmet. It's simple to use, should fit to any vented helmet, and the batteries last for ages. Also, I haven't had any issues with water ingress like we had on previous test models. There is some tough competition out there, though.
We last reviewed the Femto Duo back in 2016 and Dave's only real concern was that, with both the front and rear lenses also being a switch, they allowed water to enter the unit in heavy rain.
In the last six weeks of testing, I haven't had any issues with that, even when testing it under the bathroom shower. I've fired water at it from all angles and even submerged the lens part of each end in water, with no ingress.
Lezyne doesn't give an IP rating for waterproofing so there is nothing to really gauge whether they should keep the water out, or to what level. Maybe I've just been lucky so far, but you could always try not to use the switch in the rain, and check for water inside the lens after riding – at least that way you can dry them out before any damage is done.
As for the light itself. Well, it's basically a front and rear Femto light, joined together by way of a composite bracket which allows you to run a Velcro strap through it so you can attach it to any vented helmet. Once in position, the light is held in place securely.
Operation, as I've mentioned, is controlled by way of pushing the lenses. Press and hold to turn them on or off, and apply just a small press to scroll through the modes.
Each 'end' has three Flashing modes, each one faster than the previous one, plus Pulse and Solid.
A run-time of 30hrs is given for the constant Solid mode, and 60hrs for anything that flashes or pulses. It's hard to gauge, as the Duo uses two CR2032 batteries either end, which I know from experience can be affected by temperature – the cold can shorten their lifespan.
The front light pumps out 15 lumens, the rear 7 lumens. Both ends of the Duo can be operated individually, so you can run whatever combination of flashing or constant pattern you like.
The front light puts out more light than you'd expect, and though you wouldn't (and couldn't) use it as a main light, it's bright enough to be seen on the floor, and I found it handy to be able to glance back at the cassette if I wasn't sure what gear I was in on very dark roads.
The rear one is still bright enough to be seen by, helped by the fact that it's elevated.
The Femto Duo is priced at £28, which is in line with something like Brightside's Topside Helmet Light at £29.99.
That's capable of putting out up to 100 lumens, though, while still offering decent burn-times, and it's rechargeable. It also gets an IP65 rating, meaning it'll cope with heavy jets of water. That's a lot of light for the money, and makes the Femto Duo look pricey and a little outdated in comparison.
Topeak's Headlux isn't that bright, but as a be seen light it still does a decent job. It also uses CR2032 batteries and offers good burn-times. It'll set you back £18.99.
Overall, the Femto Duo is a decent performer, as long as it continues to keep the water out. It's got some tough competition for the money, though.
Compact 'be seen by' light, but it's not the best value out there
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road.cc test report
Make and model: Lezyne Femto Drive Duo
Size tested: 15lm front, 7lm rear
Tell us what the light set 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?
Lezyne says, "Two-in-one safety light integrated into a versatile helmet mount. The Lezyne Femto front and rear light is coupled by a composite matrix junction. Compatible with nearly all vented-style helmets. The Lezyne Femto Duo's LEDs are housed in a super compact, lightweight and durable machined aluminium body. High-grade polycarbonate lenses provide side visibility and double as the power button."
It's a decent light that puts out more illumination that I was expecting.
Tell us some more about the technical aspects of the light set?
* Small 2-in-1 safety light.
* Combined front and rear light coupled by composite matrix junction.
* LEDs are housed in machined aluminium body.
* Powered by two CR2032 batteries.
So far, so good. I haven't had the water ingress issues we've seen before.
Battery life is good considering it uses CR2032s.
Tell us how the lights performed overall when used for their designed purpose
The Duo gives out more light than I expected, and it fits securely to the majority of helmets.
Tell us what you particularly liked about the lights
Easy to use.
Tell us what you particularly disliked about the lights
Not as powerful as similarly priced competition.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
The Brightside offers much more light and performance than the Femto Duo for basically the same money, while the less bright Topeak mentioned in the review is nearly a tenner less.
Did you enjoy using the lights? Yes
Would you consider buying the lights? Probably not, especially at full price.
Would you recommend the lights to a friend? Yes
Use this box to explain your overall score
The Femto Duo is brighter than expected and it's well made. It's up against some tough competition for the money, though.
About the tester
I usually ride: This month's test bike My best bike is: B'Twin Ultra CF draped in the latest bling test components
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, club rides, sportives, fixed/singlespeed,
With 20 years of road cycling and over 150,000 miles in his legs it's safe to say Stu is happiest when on the bike whatever the weather. Since writing his first review for road.cc back in 2009 he has also had a career in engineering including 3D-CAD design and product development, so has a real passion for all of the latest technology coming through in the industry but is also a sucker for a classic steel frame, skinny tyres, rim brakes and a damn good paintjob.
His fascination with gravel bikes is getting out of control too!