Knog Plus Twinpack

The Knog Plus Twinpack lights are impressively bright, weigh the same as a bag of crisps and clip/unclip in seconds. Some lower than claimed burn-times and slightly iffy finishing are the only potential issues, though they could be just a little cheaper too.

• Pros: Low weight, clever magnetic clip, bright, good choice of modes
• Cons: Short life on steady burn

To be clear, the burn-time issue was limited to one mode, but as that was 'steadily-on', I found it an issue. I prefer a constant light on the front – to assuage those drivers who claim flashing lights makes it hard to judge distance, and to avoid giving myself some kind of strobe-induced fit. Knog claims 2hrs solid light, but this 40-lumen white COB (Chip On Board) light only managed around 1hr 45mins before dying. The low battery light comes on at 1 hour.

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Fortunately there's a workaround. While the fast Strobe is claimed to last 8.5hrs it's very distracting, as is the arrhythmic Fancy Flash (10hrs). Luckily, Pulse – which fades up and down smoothly from full power – gives at least the claimed 4.5hrs without running dry, and is noticeable without being distracting.

The final mode is Eco Flash, which allegedly gets a whopping 40hrs from one charge. As it's off more than it's on I never felt like relying on it. Front and rear offer the same options, with a quick press of the button cycling modes and a long press for on/off. A useful red indicator warns of low battery levels.

While the rear light has half the output at 20 lumens, it's still impressively bright, even in daytime. On overcast days, it bounces noticeable light off frames and even dry, unshiny tyres if you peer back to check it. I used them routinely to be seen in the day, and found them highly visible whatever the weather.

The fittings are great. The selection of silicone bands makes finding a suitable size easy, and the tiny brackets fit in seconds. The lamps then slide in and secure by magnet. It feels precarious at first, but I still have both lights (rear mounted vertically, front horizontally) despite routinely spanking them over truly broken Welsh winter roads at considerable speed. Their tiny mass – they're 12g each – means it would take a severe shock to accelerate them beyond the magnet's force.

The main bodies are also hooked like pen caps to slip over pockets or straps, and made of slightly flexy rather than brittle plastic that can take the odd knock. The air pockets in whatever fixes the lens to the body don't look good, but I've had no leaks or breakages yet, despite plenty of vibration and biblical rains.

The USB contacts are covered when the lights are in the mount, but not sealed, so the rear in particular can get dirty. A wipe with a finger is enough to clean the thin metal foil – plugging them in to charge without doing so (they're a male fitting, so no cable) will lead to rapid wear.

These Knogs charge from empty in around 4 hours (in a phone charger plug), and a bright light makes it clear when they're full. And really, that's the Knog Plus Twinpack all over: they're quick, easy and effective, plus they really are light – in every way.

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There's no shortage of 'be seen' bike lights, but few are this small and light. Electron's Pod USBs are great, for instance, but twice the weight and £13 more at £45. They do burn a little longer, however. Even Guee's dinky, simple COB-X lights weigh twice as much, and are £35.

> Buyer's Guide: 16 of the best rear lights

Go much lower on price and output/clamp design tends to suffer, though there are exceptions. Lifeline's USB LED set stands out from a sea of similar designs with good burn-times, great build and a wispy 35g weight. The few features they have barely work, but you might not care at £20.

Verdict

Bright, exceptionally light and super-simple to use, these tiny USB lamps are limited only by burn-times