I just received my TK70 light a week ago and have formed some opinions. I struggled for quite a while over which triple XM-L to buy but finally settled on the TK70.
For those of you that are still considering this, I wanted to share my advice.
The primary advice is that the lumens will probably NOT be as impressive as you expect them to be. Secondly, beam pattern is particularly important for usability.
Remember that it takes about 4x as many lumens for a flashlight to appear twice as bright to our eyes. This is because of how our eyes work. You can easily test this by using one of your multimode lights. When you go from 3 lumens to 30 lumens for example, does it REALLY look 10x brighter? Not really. More like 3x brighter.
Most of you likely have an MC-E, SST-50, or even XM-L light already. So you already have a 500 lumen flashlight or better. Consider that your Triple XML of choice is going to be 4x the lumens but will only LOOK twice as bright! Thus, you may be disappointed if not ready for this fact. I was actually disappointed with the TK70 output because "2300 OTF lumens" simply sounds better on paper than it does in real life, relative to my 600 lumen lights.
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Secondly, what makes a big light impressive is how well it throws and thusly how far off you can see. While I have never been a fan of pure throw lights, I do understand that for a huge triple XM-L the intent is usually to illuminate a large area that is fairly far off.` Remember that the level of light on an object falls off pretty rapidly over distance. A flashlight with a high beam angle is basically dividing all its lumens by the area of a circle (pi x Radius squared), and the radius of the circle is dependent on the beam angle of the hotspot and the distance. Thus beam angle is quite important.
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To assist with your effort, I have two forum posts with beamshots from various flashlights. use these to compare!
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Why I chose the TK70:
The TK70 is much more expensive than the cheaper offerings. One can get it for about 200 bucks shipped from say goinggear with the 11% off coupon code. Some have found it cheaper from HKgood or something but this was the best deal I could find including shipping.
The TK 70 has a very large head with deep reflectors. As such the beam angle is very impressive. It throws like a beast and illuminates extremely far off. It out throws the SR92 and rivals the SR91. In my tests, it can light up trees and obstacles that my 600 lumen MC-E/SST-50s don't even touch. Putting 4 of my 600ish lumen lights together would be brighter, but still wouldn't light up that particular tree.
It still has plenty of flood and lights up an area quite nicely.
Build quality is very good. Unlike the cheaper offerings, I can expect the TK70 to have a very good driver and not poop out on me. This doesnt justify 4x the price exactly, but it IS a factor to consider.
So far the TK70 has been shown to be a reliable light based on topics and forums Ive read.
It is a legalized weapon pretty much. Not to go into this topic deeply, but Ill bet most people would feel safer walking around with this thing, compared to the grenade-looking DRY/Nitecore or long skinny 3x18650 trustfire. But it is not modified to be a weapon, doesnt look like a police baton, or any other of those factors which could theoretically be problematic if you did however unlikely, get into an incident.
The thermal mass of this thing ensures that you can run it for an extended duration without getting hot.
Finally, the light modes are well done. The low 20 lumen mode is enough to not ruin your night vision but enough to see decently if walking around the house at night for example. The 300 lumen mode is about equal to a strong RCR123 keychain light. Good for walking after dark or general purpose. The 900 is when you really want to light up an area, but you can sustain this level indefinitely. Then the turbo of course for maximum output.
Hope this is helpful on your search!