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Fenix Extended Runtime Kit for TK75 Flashlights (AET-TK75-BK)

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Fenix Extended Runtime Kit for the TK75 Flashlights

Increase Your Light's Runtime

The Fenix Extended Runtime Kit is made up of (1) tube, or extender, and (1) battery magazine, which holds (4) 18650 cells (not included). The simple extension kit is designed for use with the Fenix TK75 LED flashlight and enables users with the ability to increase a light's performance. The TK75, on its own, runs on (4) 18650 batteries and can last for up to 270 hours, when in Low mode. The extended runtime kit doubles the number of batteries used from 4 to 8 cells and therefore increases the light's overall runtime. In fact, users can combine up to 3 kits together to create the ultimate long-lasting flashlight. As an added bonus, the Fenix extension kit offers a flat base for effortless tail-standing. Feel free to use your improved light as a candle during a power outage or a storm. Please note that in addition to elongating the runtime of the light, users are also lengthening its body.


Extended runtime kits position the batteries in parallel, increasing runtime while leaving voltage unaffected. However Fenix recommends using no more than three extended runtime kits per flashlight.

Features and Specifications:
  • For use with 4 x 3.7V 18650 Lithium-ion Batteries (Not Included)
  • Reverse polarity protection
  • Over-Charge & Over-Discharge Protection
  • Dimensions: 3.9" x 2.1" (100mm x 52.5mm)
  • Weight: 5.7 oz. (162.5g) excluding batteries
6 Reviews
67% (4)
33% (2)
0% (0)
0% (0)
0% (0)
By ron
Lynnwood, WA
Good but could be better
October 31, 2018
I use this kit with my Fenix TK75 (2018). The fit and finish are what we expect from Fenix... perfect.

For 6 months this has been providing an outstanding light with the ability to last thru a whole night. My only criticism is that it doesn't provide the ability to charge the batteries in the cassette as the TK75 (2018) does. Which means needing a separate charger or the time it would take to swap the batteries into the original cassette to charge them. Unfortunately this can take more time than we have daylight available to us in the Winter.
Alpharetta, GA
Long run time
February 7, 2017
I use it with my TK75.
It realy work very good.
By Steve
Extended Run Time Extension
January 2, 2017
Fits as it should, The light will operate with half a load of batteries, I found out as the batteries were getting their first charge I tried it . With full load of batteries the light gives the impression it is slightly brighter, I am still running on the first charge, unknown run time
ProsFit n Finnish
ConsIf you can call it a negative it adds length and weight I like the added length and weight is not a issue
By Robert
Denver, CO
Double the Run Time of your TK75
May 7, 2016
These are great. an easy way to double or even triple the run time of the TK75. I bought 2 of them as the manufacturer says
adding more extenders then 2 does not really increase the run time much more..
ProsBuilt very well, has the same grip as my TK75 2015 edition has, greatly increases runtime. Good price. (saw on eBay for $50).
By CoosaTotah
Good Construction
April 17, 2016
Good construction. Simple to attach to the TK75.
ProsGood construction. Simple to attach to the TK75.
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Fenix Extended Runtime Kit for TK75 Flashlights (AET-TK75-BK)

  • $29.95
  • & Free Shipping On Orders Over $50
  • In Stock