I want to go ahead and switch out the driver on my surefire xmlTt zoomie that I bought off of ntg. It looks like it uses a 20mm driver. I’m looking for something with 3 modes or less. I don’t know if there are any 2 mode drivers? The flashlight runs on one 18650 cell. Would a direct drive or FET driver work?
http://intl-outdoor.com/17mm-to-20mm-brass-ring-driver-adapter-2pcs-p-804.html
An AK47 driver (17 mm) has 2/3 mode options, selectable via soldering the stars on its backside.
DD/FET will overheat a single XML emitter. You can mod an AK47 into a FET driver comfychair-inspired quick+cheap+lazy single-sided 17DD FET-driver (poor man's nanjg92)
That’s what I was thinking about FET for that led. Those adapter rings are very cool! I noticed that most drivers are 17mm. I was hoping to push higher amperage on high mode, mostly to show off. Then use lower modes for sustained use. I was bragging to someone at work that I was going to modify the light. Maybe I can sucker some one else into joining the led hobby lol.
edit: would this one be a good fit? 2800ma on hi and 840ma on med. I’ll definitely need to get a better battery.
https://www.fasttech.com/products/1612/10001683/1122302-8-amc7135-4-group-25-modes-led-flashlight-driver-c
There's not many people owning or even modding Surefire's over here at BLF (the price/performance ratio is generally considered way too high), out of curiosity, would you mind posting a few pictures of how it looks inside while modding it?
I lied, its an xml U2. This light’s been opened before. The threads on the LED retaining ring were damaged and you can see the piece of solder that dripped onto the led board. You can also see the thermal adhesive left on the back of the LED board. I compared the LED to the photos in the fake Cree awareness thread and it appears to be genuine. The inside is hollow with a lip that the led and driver sits on. There isn’t much contact area to draw away heat and it might benefit from an aluminum disc to lay flat against the LED board along with some thermal goop.
Oops… Not sure fire, it’s ultra fire. Darn those knock off companies that make products that sound like the $$$ brand names
From the pictures, I had already guessed! 
My guess is that it has not been modified before, what you see is the sloppy work of the manufacturer. And even though the board says it is an U2, I give you 99% that it is not a U2 but lower bin. It looks like a real Cree led though.
Oh, it’s an ultrafire zoomie - like this one generic 'ultrafire T6' xml2/nanjg105c mod ? Don’t put too much effort into modding it, those lights don’t have lumen output as impressive as lights with proper reflectors.
My recommendation would be to buy a convoi flashlight (or a convoi host if you want to practice modding) or wait for the next group buy.