In my opinion the essential exploration and emergency torch, the following is my review of Fenix Light TK40 LED flashlight. The disclaimer is that i am still rather new and an amateur to the world of quality lighting, but i will do my best.

My Story (of no real significance to review)

I have been looking into flashlights since my last year of undergrad studies, preparing for a backpacking canoe trip in the Ontario lake-lands. Not satisfied with either cheap alternatives or the ridiculously expensive Surefires, i eventually came across Fenix lights. To be fair, Fenix lights aren't exactly cheap, but i've read nothing but positive reviews and was blown away by the quality and value of my eventual purchase, the LD20(Q5). I later applied and became a small authorized dealer of Fenix lights. I can only afford to stock a few select models at a time, more to satisfy my own enthusiast cravings than to an attempt scrape together some extra cash. It was then that i had the chance to try and be amazed by Fenix's behemoth, the TK40. (I will try my best to remain impartial in my review and in my defense, i bought before i dealt)

(graphic pulled from Fenix's official site www.fenixlight.com)

History/Brand (of little significance to review)

"Made in China" is not a stamp commonly associated with the quality or substance of the product but Fenix commands more than simple cheap dismissal. Fenixlights Limited was established around 2004, and has since focused producing professional flashlights based on current Cree LEDs, moving from the professional/tactical to include exploration, everyday/pocket sized, and camping/general outdoor use lights. The first light produced by this young group of sure-headed business men and engineers, the L1, was an instant success with enthusiasts and professionals. Tightly regulated sales policies, continued emphasis on solid quality and innovative circuit design, and frequent updates kept Fenix in fair competition with the leading professional flashlight brands. The only cheap aspect of Fenixlights (aside from the E01 {others might disagree}) may be their english and somewhat tacky and overtly designed advertisement graphics.

(updated L1 model graphic pulled from Fenix's offical site www.fenixlight.com)

Technical Summary

• Cree MC-E (quad core) LED, 50,000 hours lifetime
• 2 modes, 8 outputs
   - primary output:
        --> Turbo (630Lumens, 2h) --> Low (13Lumens, 150h) --> Mid (93Lumens, 20h) --> High (277Lumens, 6.8h)
   - strobe mode:
        --> Strobe      --> Slow flash      --> SOS      --> Fast flash
• Uses 8 x 1.5V AA (Alkaline, Ni-MH, rechargeable) batteries(4 AA batteries is available in emergency)
• Length = 208mm, Diameter (head) = 62mm, Weight = 284g (without batteries)
• T6 aircraft-grade aluminum body
• Type III hard-anodized black finish
• Waterproof to IPX-8 Standard
• Anti-reflective coated glass
• Push-button tailcap switch
• Included accessories: shoulder strap, two spare o-rings, rubber switch boot, metal key ring, manual, plastic carrying case


The first impression holding the TK40 with batteries all loaded in hand is its solid built. Using 8 AA batteries instead of the more popular 3V CR123A or 4.2V 18650 widens the TK40's diameter to a size that reminds the amateur me of old Maglites that run on hulking D batteries. In this regard the TK40 feels more akin to a well designed bludgeon that will last me a life time, than a professional flashlight that i'd carry on my person. In all fairness, the TK40 is not all that heavy. Its aluminum walls are actually on the thinner side compared to other light, i imagine an attempt to reduce the width and weight. Now, i have Yet to used the TK40 as a club but would bet that it'd do pretty well since experience dropping my Fenix LD20 from moving bikes and down rocky hills did little more than mar the anodized black finish.


The head and tail unscrews smoothly enough and the threads fit with very little slack. O-rings on either joint provides the IPX-8 standard waterproof rating and, as with all o-rings, are likely the first parts of the flashlight that will need replacing in regular use. Good thing that 2 spare o-rings are provided by Fenix. The hard thing is not to misplace them before the time comes.

All contacts are gold plated and will work even if the head and tail are very loosely attached due to 2 springs, one on the tail and one on the battery cage/magazine. Though there are no markers, common sense is enough to prevent loading the battery magazine the wrong way, with both springs touching. There are no reverse current protection on this Fenix and i've yet to try it, but the contacts looks to be set up so that reversed loading of the magazine will not complete a circuit. The magazine itself is very solid. Some complained that the batteries tend to pop out of the magazine easily in the earliest TK40s, but the later production runs has added plastic molds to the negative end springs and the AA batteries now fit quit snug. 4 (higher quality NiMH) AA will suffice to turn the light on in emergencies, but the current draw will be very heavy on just 4 and the batteries will run very warm. The 4 batteries must also be loaded in series to work. (The debate between the pros and cons of AA batteries versus more professional varieties will not be included in my review, as i am yet knowledgeable enough in the matter to add anything new to the topic)


I suppose the intention is to simplify the design while retaining multiple functions, but one tail button as sole selector for 8 modes was difficult to figure out intuitively. A quick scan in the short manual and a couple of minutes later however, was enough to get used to the controls.
   - One click turns it on in the last setting used
   - Hold the button down (and light off) for 1 second advances to the next mode
   - Double click to switch to the strobe mode corresponding to the brightness level
The memory function (turning on in the last mode used) is quite helpful in avoiding excessive scrolling through brightness levels to get to the most commonly used mode. In this respect, Fenix's decision to move the infrequently used strobe modes out of the regular cycle was a smart one. The trade off to not having to cycle through 4 different strobe modes before going from brightest to dimmest is that specific strobes modes are tied to specific general modes and are arguably harder to get to. There is a noticeable flicker when changing from the brightest back to the lowest setting, which i think is caused by the circuit releasing a small bust of high current before stepping down. The flicker seems to be there for the SOS mode also.

Brightness and Runtime:

This is where the TK40 really shines (pun intended). 630 Lumens is on par with car headlights yet the TK40 runs on AA batteries! Although 2 straight hours on the turbo mode may be slightly optimistic, i did get 1.5 hour plus without any problems using old rechargeables that may not have been at optimal capacity. At the lowest 13 Lumens setting the TK40 will run for close to 7 days straight, which should be enough for a solid month of generous nightly use.
The following are pictures of the TK40's general modes taken in a 10-metre-long garage. The aperture is set to 2.5 and the exposure to 1 sec on the left column and .5 sec on the right column. The last picture of both columns are with the double 60 Watt garage lights turned on.
The beam is decent and the dimmer centre due to the quad LED core configuration is not visible after further than 2 metres out. The corona is quite small and transitions to a very useful spill. The tone is on the cooler side, not unlike the fluorescent white lights lighting the garage. I am not able to produce current draw charts yet, but i feel that it is suffice to say the TK40 is more than suitable for everyday, professional, or emergency use with its range of runtime and brightness levels.


I have to admit that i am still an amateur when it comes to knowledge, and perhaps taste, in the field of quality flashlights. For me, the convenience of rechargeable AA batteries outweighs the advantages of pricier 3 volts plus professional alternatives. And, in the 640 Lumens TK40, there are definitely no sacrifices in brightness or quality. Holding the TK40 reminds me of the old Maglite giants that i relied on as a kid, except there is now the option of annoying the hell out of the neighbors with high speed 640 Lumens strobe. Fenix in my opinion is the Thinkpad of flashlights.

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