Alright, I've seen questions on a couple of forums off and on about these flashlights, so I thought I'd post up a little mod I did to make a crappy flashlight in to actually a pretty good one. I also think this is a mod that anyone can do.
The light can be seen here - https://budgetlightforum.com/t/-/626
Here's a eBay link to one of them - http://cgi.ebay.com/TECHLITE-LUMEN-MASTER-TACTICAL-LED-FLASHLIGHT-w-STROBE-/260706401215?pt=US_Flashlights&hash=item3cb34ffbbf#ht_1635wt_1139
The build quality of these lights is actually very good - nice threading, quality anodizing, really nice heatsinking. However, it uses 3xAAAs in a holder (yuck) and the crappy "Smart" tailswitch has a well-known battery drain issue. With a little work, you can get a very nice, very functional light out of it, though.
First of all, you need to get the right model. There are 3 models of this flashlight around.
1. First model has a half OP reflector, a Cree XR-E emitter, and no "tactical" switch, with a strobe and SOS rather than a tactical interrupt. This is further distinguishable by having pistons instead of springs in the battery chamber. You do NOT want this version.
2. The second version, and the one you want has a smooth reflector, and uses a Cree XP-E emitter. This model does NOT have the zooming head and still has the tailcap drain issue, but is otherwise not bad. The build quality (other than the plastic lens) is actually quite good.
3. The third (and latest) version has a smooth reflector, a Cree XP-C emitter, and has the twisting "zoom" head. This one again is pretty useless, but if you can find one cheap it might be worthwhile to scavenge the tailcap and extra o-rings. You do NOT want this version either.
For this mod, you will need a minimum of one of #2 above, as well as one cheap 9 LED flashlight you can find at any dollar store. I was lucky enough to find a clearance store with a bunch of these lights on for $5 each, so I grabbed one #2 and #3. For both of these mods I'll be using the model with the XP-E as the "working" flashlight.
First mod. If you take a look at this picture:
You'll see the general build of the tailcap switch. It has (in order) a thick plastic spring holder that screws in to the tailcap, the "smart" switch itself, another hard plastic spacer, and then the rubber boot cover. You can unscrew the spring holder using a pair of needlenose pliers, and then after that you can just do a hard push on the rubber boot to pop out the rest of the assembly. Don't throw anything away. The clicky is worthwhile to keep for the second mod. Underneath the tailcap assembly, you'll see a basic reverse clicky I ripped out of the cheapo 9-LED light from the dollar store. The really nice thing is that it fits in the tailcap perfectly. To get it out of the cheap light, rip off the boot cover, and then use a pen to push it out of the tailcap.
To reinstall everything, first take the translucent rubber cover from the Techlite and shave about 2/3s off of the post inside. Re-install this in to the tailcap, and then push the cheap clicky in to place. That's it. You should have *just* enough room to fit a protected 18650 battery inside. and you'll have a 160 lumen, XP-E flashlight that takes 18650 batteries for under $10.
Second mod. As easy as the first. If you take a look at this picture:
You'll see the basic makeup of the somewhat modified tailswitch I made. Since I bought two of these lights, I had an extra tailcap to play around with. Again, I removed the plastic spring holder and the the plastic spacer between the rubber boot cover and the clicky, and shaved down the post on the tailcover. I made a spring spacer out of some hard plastic I had laying around, and used one of the springs from the battery holder to make a spring contact. When I'm not using the light, I have the single-mode tailcap installed, but if I plan on taking the light out, I install the other cap (takes 5 seconds, if that).
Practical upshot, for less than $15 (closer to $13 including tax) I got a 160 Lumen, XP-E flashlight that takes 18650 batteries, with a choice of either a single mode reverse-clicky or a medium/high/strobe soft clicky, and the battery life is excellent (about 3 hours on high, nearly 7 hours on medium with my crappy ripped-out-of-a-laptop-battery 18650s).
Edit: Sorry, don't know how to directly input larger images, you'll just have to follow my Photobucket links for now.