2015 Lights Shootout

The USL-305 from Serfas has a funky name and it's not flashy with a claimed output of 305 Lumens, but it is a gem of a bike light.

We measured it at 371 Lumens and it weighs in at 116 grams with mount. The punchline is, it's only $50. Looking at the beam pattern, it's bright and concentrated enough that one can use this anywhere. It may be a lightweight for trail riding, but stick it on the helmet (with an optional mount) to complement a bar light and you'll hardly notice the weight.

So color us impressed with this $50 wonder from Serfas. Where the True series lights from Serfas seemed overbuilt at these output levels, these USL lights are just right.


Handlebar mounting is done with a quick release mount that works quite well once snug. It can be aimed left to right. The quick release lever is non-intuitive at first, as it seems to be reversed. Mounting on different diameter bars is a bit tricky, as two pins have to be aligned in the right holes to get the proper bracket size.

Beam Pattern Photo

We photographed the lights in the same location setting with the same camera settings. The photos were taken in the back yard that is approximately 25 yards long. These photos feature many objects and a distinct background to analyze detail and beam pattern. Compare all Beam Patterns here »

Serfas USL-305 Backyard Beam Pattern

Integrating Sphere Measured Lumens

This light measured 371 Lumens in an integrating sphere. Claimed Lumens by the manufacturer is 305 Lumens. The Lumen-hour graph below shows how the light performs over the first three minutes of its battery cycle. Compare all Lumen Tests here »

Serfas USL-305 Lumen Chart


  • 371 Lumen light output is brighter than claimed
  • $50 price delivers a lot of value
  • 116 grams and small form factor makes it very useable for a variety of purposes


  • There's no longer any accessories like a charger or helmet mount at this pricepoint


  • Price: $50
  • Claimed Lumens: 305 Lumens
  • Measured Lumens: 371 Lumens
  • Lumens per $: 7.42 Lumens
  • Lumens per gram: 3.20 Lumens
  • Time on High: 1:30 Hours
  • Charge Time: n/a Hours
  • Mounted Weight: 116 grams
  • Category: Flashlight/Commuter

Overall Rating

5 Flamin' Chili Peppers
5 out of 5 Flamin' Chili Peppers

For more information visit www.serfas.com.

This article is part of Mtbr and RoadBikeReview's 2015 Lights Shootout. To see all the bike lights tested CLICK HERE.