UTLA-7 Thunder Blast Tail Light (40 Lumens)



Quick Overview

“BLAST” Audible Low Battery Indicator

Coming up with ways to make you safer on the road, when using Serfas lights, is a top priority. NEW for 2016, our “BLAST” Audible Low Battery Indicator emits a loud 85 Decibel signal when your light battery gets under 10 minute runtime in that specific mode.

How It Works

  • When the battery reaches 10 minutes of runtime, in its current mode, the light will emit a long beep followed immediately by a short beep. Sound will continue every minute.
  • When the power button is pressed it will put the light in the next longest running mode & it will restart the battery low alert until 10 minutes of runtime in the mode is reached. Repeat as necessary. Example: Going from highest mode to lowest mode at first beep could extend runtime up to 5 times.*
  • Light will emit beep sound repeatedly when last minute of runtime in the current mode is reached.
  • While charging the light the power button will blink blue. When full charge is achieved light will beep to notify charging cycle is complete.
  • Light emits a beep when power button is pushed & light goes from mode to mode.

Thunder Blast Tail Light User Manual




  • “Blast” Audible Low Battery Indicator Alerts Rider Of Low Battery
  • New Body Design Easily Fits Aero Applications
  • Low Flash Lasts Up To 14.5 hours
  • Extra Long Mounting Straps For Endless Mounting Options
  • Solids Modes: High (40 Lumens): 2.25 hrs & Low (10 Lumens): 7.75 hrs
  • Flash Modes: High (40 Lumens): 4 hrs & Low (10 Lumens): 15.25 hrs
  • Weight: 48 Grams Without Bracket
  • Battery: USB Rechargeable Li-Polymer

Thunder Blast Tail Light User Manual

Additional information


Black, Blue, Clear, Red, White

5 reviews for UTLA-7 Thunder Blast Tail Light (40 Lumens)

  1. Keith D.

    Every tail light I’ve owned prior to the Thunderblast seems like a joke now. In fact, many of the headlights I’ve owned dont compare to the Thunderblasts output. My only concern is that on high, motorists or trail riders behind me might get blinded by the power – thats a happy problem in my books as the lights plenty strong to run on low power. I dont worry anymore about not being seen by motorists.

    Thanks Serfas, you guys rock.

  2. Alex

    I’ve been using this light for a while so I think now would be a good time to post a review. First the positive. This light is bright! Even the low mode is bright. I like that it is a long bar not just a spot as this makes you more visible from a distance. I like the rubber band mounting system. It’s very flexible and if you break one, it is trivial to replace it.

    The one thing I really don’t like is that it takes a long time to recharge the light. I have another, smaller less bright, tail light that that gets the exact same use, and it charges in about a 1/2 hour. This light takes more than 2 hours to charge. My super bright, 1200 lumen, headlight that lasts longer on the highest setting, charges in the same amount of time.

    Nit picking now, but I would prefer if the charging port was located so that you could charge the light without removing it from the bike. I also wonder if going with a USB charger was a good idea. Yes, it is super convenient since most of us already have a bunch, but it seems that a USB charger can’t supply enough current to charge this in a reasonable time.

    With all that said, I really like the light and even with all the drawbacks I mention, I would buy this light again.

  3. SJ

    Just pulled it out of the box, and it is BRIGHT. Form factor is nice, I put it on the seat stay;

    -I’d like it better if it was angled so that it’d make sense on the seat stay.

    -I wish the usb port was accessible when installed on the bike (probably more weather protected where it is though)

    -What is the connector type? Why isn’t it micro-b usb like everything else in the world (cellphones etc) instead of Mini-b (i have no idea what else this is for)?

    -It is super bright

    -‘long hold’ turns it off

    -it looks cool

  4. Ben

    Great looking light, fitted really well on an aero seatpost. Cant find anything else that fits so well on the bike. Unfortunately got wet on first wet ride and died. Cant bring myself to spend $50 bucks on another and have it die…. 🙁

  5. Lauri Scharf

    Awesome brightness, excellent runtime and durability. Only complaint: The straps are too easy to lose. Since there’s no other way to mount the light, the straps may as well be permanently (or at least more securely) attached.

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