The Knog Frog V3 Light Twinpack makes a useful addition to any bike, either as backup to more powerful lights or alone if you don't need lights for seeing with. While the battery life has a very impressive claim, the majority of the modes yield only an average-to-decent outcome.
If you're happy to look at front and rear lights separately, check out our guides to the best front bike lights and the best rear bike lights, for more options.
As someone who has found an increased need for riding with lights at all times in recent years, with the standard of driving in the UK, I found the Knog Frog V3s a great second set of lights for those questionable visibility days. They're super easy to just chuck on the bike, and useful no matter what the weather's doing.
When I saw the shape and look of the Frog V3s, I'll admit I was sceptical and thought they were going to be very similar to those awful, super-cheap offerings many people will have somewhere buried in the back of their shed. The minute I turned them on, however, I knew that wasn't the case. This is a quality set of lights with a surprisingly powerful output considering their size.
The thing that stood out most to me was the amount of light projected sideways, making me a lot more visible to motorists coming towards me from an angle, rather than just a straight beam forwards and backwards.
Light and easy to mount
At only 20g per light, with a simple design, they're easy to attach and are so unobtrusive you can almost forget they are on your bike.
The way they mount means there's no possibility for rotating them – so the front has to be mounted onto the handlebar, it can't be mounted on the stem like most bigger lights can, but it's not a huge concern as it's so small.
The rear was slightly more awkward for me to fit, personally, as I have quite large legs, and so I had to be more careful with placement on the seatpost so as to avoid catching my thighs on the light.
Battery life & charging
The claim of up to 50 hours of run-time between charges got me really excited, but this applies to eco mode only.
The first time I used these – before reading all the details – I put them on to the Full Bright flash mode, which is what I would choose to use almost all the time. This is a 40-lumen setting with a short, full blast. When they only lasted around 10 hours, I was a bit disappointed.
Having read the info more carefully since, it's the Eco flash modes (10 lumens for the front light, and 4 lumens for the rear) that give those long run-times. And not 50 hours, but a claimed 80 hours for the front, and 60 for the rear, which is amazing as a fit and forget option if that's all the illumination you want.
The lights are easily rechargeable by USB-C, in the claimed three hours from empty. I did think a faster charge could have been achieved, with USB-C, but it wasn't too much of a drawback for me.
The battery indication on the Knogs is okay, but can only be seen when the lights are off (or when turning them off), which is a bit of a downside. One short press on the button lights up a percentage of the LEDs, depending on the charge level. Not being able to see any indication while the lights are on is a shame, and in the worst case could lead to you not knowing they are running out of battery, and then being stranded with no lighting.
Each light has nine modes, with just two – high and low – constant outputs (18lm/4hrs and 3lm/20hrs for the front; 7lm/3hrs and 1lm/15hrs for the rear).
The rest are a bunch of flashing modes with different sequences, depending on what you're looking for, including the highest output Full Bright (40lm front, 20lm rear). There is also a 'Back to Front' mode and a 'Back to Front' mode, which flash in the middle and dissipate outwards, or vice versa, using the array of LEDs. Or there's a 'Side to Side' mode which bounces the light from one side to the other, and a 'Rotation' mode which constantly sends the light from right to left.
The one button is a nice, easy way to interact with the lights, needing a long press to turn on, and a single press to cycle through the different modes. It can be a little finicky to hit the actual switch sometimes – it's quite a small surface area under the silicone, so can be easy to miss occasionally, especially if you're wearing thick winter gloves.
Value and conclusion
At £46.99 for the pair, they're surprisingly expensive for what they offer, when it is possible to buy a pair with a much brighter front light and be able to ride in the dark for not much more money.
Lezyne's pairing of a Mini Drive 400 front and Femto USB Drive rear costs just £3 more, for example, and will enable you to see where you're going and give you 15 hours of run-time for the rear in a daylight flash.
And while the Knog + Twinpack Light Set isn't quite as funky looking as the Frog V3s, it has very similar specs, for £34.99.
Overall, I'd say the Frog V3s make a good second set of lights, being light and easy to use, but they are a bit pricey for that, and unless you only ride on street-lit roads you'll need something brighter for seeing with.
Very small lights that work well, but expensive for the output
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Make and model: Knog Frog V3 Light Twinpack
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?
Knog says: "Taking cues from Knog’s more advanced lights, Frog is designed with Chip on Board LED technology, enabling a high intensity light that's compact, low profile and packed with features."
Tell us some more about the technical aspects of the light set?
Punchy 40 lm front & 20 lm rear output
Integrated flexible mounting system
9 eye-catching modes
Water resistant with IP65 rating
Super lightweight at just 20 grams
Curved lens provides side illumination
Simple one-button operation
Available in 6 fun-loving colours
Rate the front light for quality of construction:
Rate the rear light for quality of construction:
Very well built, solid feeling lights.
Rate the light set for design and ease of use. How simple were the lights to use?
Very easy to put on the bike and so small and light it was easy to forget they were on.
Rate the front light for the design and usability of the clamping system
Rate the rear light for the design and usability of the clamping system
The front light clamps easily onto handlebars, the rear is a bit trickier; if it is mounted on the seatpost it can foul with legs as it sits to one side.
Rate the front light for waterproofing. How did it stand up to the elements?
Rate the front light for waterproofing. How did it stand up to the elements?
A waterproof flap over the USB-C port meant there were no issues with any water ingress.
Rate the front light for battery life. How long did it last? How long did it take to recharge?
Rate the rear light for battery life. How long did it last? How long did it take to recharge?
The claim of up to 60 hours between charges is true for eco mode, but six to seven hours is average for most of the others. They don't charge particularly quickly either, at three hours from empty.
Rate the front light for performance:
Rate the rear light for performance:
As lights to be seen by they are great, with excellent side visibility.
Rate the front light for durability:
Rate the rear light for durability:
So far I have had no issues with them. The only potential problem is snapping the band that holds them on, in which case the lights would be useless. But there's no sign of that happening.
Rate the front light for weight:
Rate the rear light for weight:
At 20g each, these are about as light as you're going to get for something worthwhile.
Rate the light set for value:
These lights are surprisingly expensive; you can get much bigger and brighter lights for a similar price.
Tell us how the lights performed overall when used for their designed purpose
They achieved their purpose of being small, unobtrusive lights to be seen with very well.
Tell us what you particularly liked about the lights
I liked their fit-and-forget nature.
Tell us what you particularly disliked about the lights
I wish the battery life was longer for the more useful modes.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
The price is similar to a set from Lezyne that includes a 400-lumen front light, with 15 hours of run-time for the rear in a daytime flash.
Did you enjoy using the lights? Yes, as a second pair.
Would you consider buying the lights? Not at this price.
Would you recommend the lights to a friend? Not for the price.
Use this box to explain your overall score
These lights achieve what they are designed to, but the price is high for the output.
Age: 22 Height: 174 Weight: 72
I usually ride: Canyon Aeroad My best bike is:
I've been riding for: 10-20 years I ride: Every day I would class myself as: Semi pro
I regularly do the following types of riding: road racing, commuting, touring, club rides, fixed/singlespeed, mtb,
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