USL-6 Thunderbolt USB Headlight


SKU: USL-6 /

Quick Overview

Durable Silicone Rubber Encased Light Body

Very Bright For Its Size – 90 Lumen Output

Highly Versatile Mounting Possibilities

4 Lighting Modes

Built-In USB Charging

Water Resistant Construction



USL-6 User Manual & Runtimes


Limited Lifetime Warranty
Serfas® warrants to the original purchaser that the product is free of defects in material, construction, and/or workmanship for the lifetime of the product.

Battery Warranty – One Year Coverage
Serfas® batteries are covered by a 1 year warranty from the original date of purchase.


  • USB Rechargeable
  • Charge Indicator Light
  • Includes Longer Strap To Allow More Mounting Options
  • Removable Straps Allow Endless Mounting Options
  • LED Strip Creates A Non-Directional Flood Of Light


  • Modes:
    • High (90 Lumens): 1.5 hrs
    • Low (30 Lumens): 4.25 hrs
    • High Flash (90 Lumens): 2.5 hrs
    • Low Flash (30 Lumens): 8 hrs
  • Weight: 54 Grams With Bracket
  • Battery: 500 mAh Lithium Polymer


Additional information


Black, Blue, Clear, Green, Pink, Red, White, Yellow

21 reviews for USL-6 Thunderbolt USB Headlight

  1. Gareth

    I was lucky enough to be in Mojo bike shop in SF when the Serfas rep came in showing the new Thunderbolt lights. WOW!!!!! Both front and rear lights are amazing! Great looking and so bright! The colors they come in are great and best of all, they are USB rechargable. I would have bought both front and rear right there, but sadly they’re not available yet. Can’t wait to get my hands on a pair of these!!

  2. Steve Wilson

    I like how this light is extremely bright and spreads light everywhere, plus the multiple mounting options…I may buy another one.

  3. Mike

    I love this light. As a HEY! I’m riding here!” blinking light”

  4. RON

    Bought both front and rear lights. These lights are amazingly bright. They are easy to mount anywhere on the bike. USB rechargable (2 to 3 hrs charging gives 9 hrs of light) and lightweight. Easily removed for recharging or theft prevention. Highly recommend these lights to everyone.

  5. David G. Rodriguez

    I have been using this light for a while now. I remember when I was blown away when the representative came into our shop and showed me the new Thunderbolt. We post is light inside shop when were closed at night and we have people coming back telling us that the lights are obnoxiously bright which as a rider is a good thing

    I noticed that when I ride with the headlight mounted on my front end that the light tends to blind me a little when I lean forward to sprint. But it not a spot light. And i love the wide spead of the beam. It is a good trade-off for me.

    I love this light a lot. More than worth the price.

  6. Narciso Palma

    I NEVER write reviews unless a product is well above and beyond, or absolutely dog poor; fortunately, this light solution is the primary, and not the later

    . Everything you could want for serious riding: safety first with the super bright lighting to make sure drivers SEE you; USB rechargeable so you don’t, have to cry if you can’t, find a power outlet; mounts perfectly on my bike with as little drag as possible; many colors to chose from! They perfectly color match my bike!

    I would gladly help sponser Surfas in my next competition if I were given the opportunity, ! Good job to the men/women responsible for the creation of this lighting, system. If I needed more than two lights, Id purchase a third!

  7. Jenny

    This is my first USB rechargeable light and I much prefer it over changing batteries all the time.


    This seems brighter than my old light, and is very easy to mount and remove.


    While overall brighter, this doesn’t actually throw that much light immediately in front of me to light my path.

    It’s easy to remove. Very easy. Don’t leave it on your bike if parked in public.

    There doesn’t appear to be any low-battery indication. The light will be working just fine at full strength and the next thing you know it’s completely dead, and since it’s USB you might find yourself without a headlight and without the ability to simply install new batteries.

    There’s nowhere on the handlebars on my bike that I can mount the light, and the head tube and front forks are both large enough I didn’t feel comfortable stretching the straps sufficiently to mount the light. In the end, I used a clamp on accessory mount I had sitting around to hold the light, and it works pretty well.

    Overall, a nice low-mid range light with some quirks/annoyances.

  8. Shawn P

    We love this light for its simplicity, its brilliant power and its hassle free performance.

    Shawn P.

    SPCARBON.COM Bicycles New York.

  9. carlo

    excellent mounting system for carbon sculptured road bars!!

    very visible to other road uses!!

    usb charging!!

    been caught out twice when batteries fizzle, dont know how many hours you can get from this light so i’ll be charging this after every ride now

  10. Stephen Whaley

    I mounted this through the air flow on the front of my bike helmet so that it would illuminate the path wherever I turn my head. It doesn’t have a long focal throw, but it still did a great job. I ride on a golf course at night which tends to be windy, hilly, and dark. This helps me see a little farther down the path to where I’m going. At the same time I’ve got a handle bar mounted light that keeps the path lit. I wasn’t fully charged so the thunderbolt quit at about an hour on my first ride (full strength.) A longer battery life at full strength with be appreciated. And a warning/dimming as the battery drains would be helpful. At intersections I noticed people notice me. Great safe light!

  11. queridiculo

    I’d give this a five star if the solid high output light would last longer than 1.5 hours. Would love to see a version with a higher battery capacity, but it’s an amazing light for what it is.

    Two thumbs up, extremely bright and a breeze to mount virtually anywhere on your bike.

  12. Linda Schack

    I bike commute to work and have both the headlight and the taillight; best lights I have ever had in terms of ease of use and brightness. Love the flexibility of the mounting system as well. The only thing to be aware of is that the lights only last a little over an hour on the brightest setting, so they need to be charged after every use.

  13. David Branscome

    Let me start by saying I’m very pleased with ALL of the Serfas products I’ve purchased. On two occasions I’ve had problems with lights. In both instances they made it right with me immediately, no questions asked. I recently purchased a pair of Thunderbolt headlights to be used as supplemental (marker) lights. I’ll be mounting these on the side of each front fork for side visibility. I am also running two Thunderbolt taillights on the side of each seat stay for side visibility in the rear. I am very impressed with the quality and brightness of my Thunderbolts. Up front I’m running their 1500 lumen headlight and the taillight is their 60 lumen model. When I hit the streets at night with all these lights turned on people will notice. I just hope the cops don’t pull me over !!! You can’t go wrong with Serfas.

  14. Barry Burke

    OUTSTANDING light! I love how I can charge it from any USB port, even in the car, with no additional chargers. The stretch mount in one of the best I’ve seen. After working in a bicycle shop for 12 years, this is hands-down, the best tail light out there. I also like the white version, on bright flash mode, as a be seen” headlight on the road. I’ve been using my pair for over a year”

  15. Darrell

    Yeah; It’s pretty sweet.

  16. Bart

    I use this as a ‘see me’ light up front when I am riding in Florida amongst all of the older drivers. In actuality, it is a ‘SEE ME’ light. I’ve used it on probably 50 rides thus far. I agree with all of the positive comments above. The only significant fault is the lack of a low charge warning. A great purchase.

  17. Bart

    I use this as a ‘see me’ light up front when I am riding in Florida amongst all of the older drivers. In actuality, it is a ‘SEE ME’ light. I’ve used it on probably 50 rides thus far. I agree with all of the positive comments above. The only significant fault is the lack of a low charge warning. A great purchase.

  18. Julian

    Got this light for Christmas 4 years ago, think I broke the body underneath the nylon but still runs strong on my 10 mileish night rides and don’t have to recharge for weeks. Would get the next gen. but I don’t think I could stand the blast feature.

  19. Michal

    I put various colour gels from a Rosco cinegel sample book and mount these on my top tube pointing straight down to light around me in purple or green so people can see my legs moving around as well as it looking cool as heck! Currently set up with a purple down/under light. I also use 2 to light up the ground (45 degree downward) beside my trailer (in orange) getting that extra visibility going on.

    This used to be my primary headlight but I started commuting in really dark areas and needed something more spot related so this light changed to “see my legs” duty.

    3 years now I think? Still going strong!

    • Serfas

      Michal, Sounds like you’re running quite a light setup! Awesome to hear Serfas Thunderbolts have been keeping you lit up at night and going strong for three years! Thanks for sharing your positive experience and we hope you continue find fun innovative ways to use Serfas lights 😀 – The Serfas Team

  20. Tristan

    Love, love loveeee this light! It has been 2.5years and it still works like new! No complaints.

  21. Leo

    I have owned this model for several years and it is as rock solid as ever. I purchased two units and primarily use them in “flash” mode while attached to the front fork blades. For predawn rides, I will turn both units onto the low-beam solid mode and supplement the lights with an additional (more powerful) lamp mounted to my handlebar. The flash mode is great for capturing the eye but the solid beam tends to disperse and not illuminate far enough up the road.

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