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Although you can use the Sigma Buster 400 to see by on dark lanes, it's a compact light that is probably best suited to being used as an emergency backup or as a 'be seen by' flashing light thanks to its reasonably low lumen output and torch-like beam. The run-times are pretty good, though, and you get a more in-depth battery life indicator than most at this price. Unfortunately, like so many others, you have to scroll through flashing to get back to the main beam.
Take a look at our guide to the best bike lights for more options, front and rear.
The Buster 400 is a dinky light, so it doesn't take up much room on your handlebar, and you can bung it in a jersey pocket or bag for emergency use.
The rubber band style strap is quick to fit to or remove from the handlebar, which is ideal if you have to leave your bike unattended. You can remove the light from the mount, but it's no quicker really.
You can pull the strap tight which gives a firm grip on the bar, so the light stays in position on all but the roughest roads.
Operation is easy: a double tap of the button to turn the light on or off (which also stops accidental operation in the bottom of a bag), and a single tap to scroll through the five modes.
Looking at the three solid modes, high gives the full 400 lumens, which Sigma says has a range of around 120m and runs for 2 hours from the 2,000mAh battery, with the next two giving 4 hours (200 lumens) and 9 hours for 100 lumens.
Like a lot of what I'd consider to be entry-level lights, the Buster has a narrow torch-like beam. It works okay as long as the roads aren't too twisty; I'd say 15mph to 20mph is achievable on the flat, but you'll be scrubbing that speed on the downhills.
You also get two flashing modes: night flash, which lasts 5 hours, and day flash, 25 hours.
Night flash keeps the LED on at 100 lumens while laying a 300-lumen flash over the top; day flash is just a straightforward 100 lumens on flash.
One annoyance is that the only way to get back to high mode once you've left it is to scroll through all the modes, including flashing – not ideal on a dark lane, but the Buster isn't alone on this.
Battery life is shown via five white LEDs on top of the light, with one dropping out with every 18% that is depleted from the battery. Once you get to 19% the last one turns red, and once it starts flashing you've got less than 5% left.
I'd say it's fairly realistic, considering variables like temperature can affect things.
Charging is via USB-C and the port sits behind a rubber cover. Overall, the Buster gets an IPX4 rating, which means it's resistant to splashes, and while I'd like to see IPX6, like some lights at this price, I didn't have any issues with rain ingress or from it being splashed by the garden hose. Keep that rubber cover closed, though.
At £39.99 the Buster is in the same ball park as others with a similar output.
It's the same price as the Cateye AMPP 500, for instance, which I tested last winter. That does get an extra 100 lumen but battery life is shorter at 1.5 hours on high. You don't need to scroll through flashing modes, though – hooray!
The Sigma is a fiver less than the Ravemen CR450, but you are getting a bit more illumination, an alloy construction compared to the Buster's plastic, a remote control, an IPX6 rating and an impressive T-shaped beam pattern. Iwein tested it last year and was very impressed.
On the whole the Buster 400 is a quality little light. It doesn't do anything brilliantly for the money, as in it doesn't trump any lights that cost a similar amount, but neither is it full of niggles. For the money, something like the Ravemen is better, but if you can find a good deal on the Buster then it's a decent option.
Not class-leading, but a decent light with a great battery indicator and burn-times for its size
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road.cc test report
Make and model: Sigma Buster 400 Headlight
Size tested: n/a
Tell us what the light 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?
Sigma says, "The BUSTER 400 gives you a universal companion on the road. On the way to work or school or on a racing bike ride, 400 lumens and 120 metres of beam range keep you out of the dark. Depending on the mode selected, you can be on the road with the BUSTER 400 for up to 25 hours, with five pre-set profiles that ensure greater ease of use. Precise LED indicators show you exactly how much charge is left in the light."
A basic spot type beam, but it comes with decent burn-times.
Tell us some more about the technical aspects of the light?
* Maximum light output: 400 lumens
* Beam range: 120 m
* Five light modes: High (400 lm), Mid (200 lm), Low (100 lm), Night flashing (300/100 lm) Day flashing (100 lm)
* Burn time: 2 h in High mode, 3 h in Mid mode, 9 h in Low mode, 5 h in Night flashing mode, 30 h in Day flashing mode
* Charge time: 3 h
* 360° adjustable bracket
* Switch on protection (double click for ON)
* Splash resistant in accordance with IPX4
* Tool-free mounting
* Charging possible during operation
* USB-C charge function
* Five-stage charge indicator, six-stage battery indicator
Tell us how the light performed overall when used for its designed purpose
It produces enough light to be able to ride on flat, dark roads at a decent speed.
Tell us what you particularly liked about the light
I liked the small increments of the battery indicator.
Tell us what you particularly disliked about the light
Scrolling through flashing to get to high.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
It's in the same sort of ball park as many lights of this size, but the couple I have mentioned in the review are brighter, and have other benefits over the Buster 400.
Did you enjoy using the light? Yes
Would you consider buying the light? No, there are better options out there.
Would you recommend the light to a friend? Possibly
Use this box to explain your overall score
There is nothing that stands out particularly about the Buster 400, but it is a dependable light that gives enough illumination to ride by on the back lanes.
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,
As part of the Tech Hub here at F-At Digital, our senior product reviewer Stu uses the knowledge gained from putting well over a 1,000 products through their paces (including hundreds of bikes) to write in-depth reviews of a huge range of kit. After first throwing his leg over a race bike back in 2000, Stu's ridden more than 160,000 miles on road, time-trial, track, and gravel bikes, and while he's put his racing days behind him he still likes to smash the pedals rather than take things easy. Although, as he spends a fair bit of his time reviewing ebikes these days he's becoming an expert in letting the motor take the strain. He's also waiting for 23mm race tyres to make a comeback!