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Serfas USB Silicone Review

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Price:  $20 List
Pros:  Light, least expensive USB rechargeable light.
Cons:  Poor brightness and beam quality.
Manufacturer:   Serfas
By Chris McNamara ⋅ Founder and Editor-in-Chief  ⋅  May 13, 2014
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  • Brightness - 40% 1
  • Beam Quality - 25% 1
  • Battery Life - 20% 5
  • Portability - 15% 8

Our Verdict

This is one light to pass on buying, as it offers poor brightness, and the beam quality is also very poor. While it's light and USB rechargeable, that isn't enough for us to recommend it as an accessory to other lights on your bike. If you want a really lightweight light, we would spend a little more money and get the Knog Blinder, which has better brightness and much better beam quality. Or, spend a little more and get our Best Buy winner, the CygoLite Metro 400.

Our Analysis and Test Results

Beam Quality

This scored a 1 out of 10 for beam quality and was one of the lowest scoring lights in this important metric. The quality of the light is quite spotty and dim.

Beam Diameter and Pattern

Serfas USB Silicone
Cygolite Metro 360


The brightness score here was about as low as it gets. This barely lit up the bike path. Compare that to the Metro 400, which can often be found for only $15 more. We measured the max distance at 17 m compared to the Metro 400s 135 m.

Beam Distance Photos

Serfas USB Silicone
Cygolite Metro 360

Battery Life

This light lasted 3.4 hours in high mode. This is slightly above average four USB rechargeable lights.


This is one of the most portable lights we tested. It is light enough to fit in any pocket and can attach just about anywhere on your bike. It does require two hands to take on and off whereas some other lights offered one hand operation.


While it is only $20 and doesn't require the hassle and cost of replacing batteries, it doesn't provide much usable brightness so we have to question its utility.


For an ultralight option, we would go with the Knog Blinder MOB The Face which has a much more visible blinky mode and better beam quality. But likely the best option of all is to spend a little more and get a really bright light like the CygoLite Metro 400.

Chris McNamara