Pros: Well made standard sized 17mm driver, works great with a single 18650 battery. Thanks to 3 AMC7135 chips, runs very bright all the way down to 3.4V or so before I could detect much dimming and still quite bright. In even a thin walled light does not make the emitter produce excessive heat. Drives R2, Q5, and Q2 emitters with amazing results. Easy install with only minor sanding of the edge and soldering is a snap. Only $1.66 per driver!

Cons: None. Zip. Zero. Some state that the number you need to buy is a con but I disagree. They just don't have enough places to put them.

Other Thoughts: This puppy will allow you to make a single 18650 push your emitter just as bright as 6-8V in the same setting. My UF 502b with a modded 11836 R2 is EXACTLY as bright as my C1 with the factory driver powered by 2 RCR123's at 8V. The caliper pic showing 17.8mm is incorrect; calipers are actually on the driver to driver packaging connection points and do not represent the actual diameter.

Bottomline: BUY SOME. As far as I know, this is the only true 1000 mA, 1 mode driver offered by DX. If you want to break free of the dependance on CR123's (expensive, ecologically unsound), or RCR123's (short runtimes, inconsistant voltages between cells) now is your chance. I'm sure if DX offered this driver in smaller amounts (say, 3-5) they would sell a lot more. I am converting every light that will take 18650 or 17670 batteries as I find the time.

Pros: These units are small (17mm diameter, 3mm (approx) height) and easy to use if you have a good soldering iron.
They provide good efficiency if Vin is close to Vout (4*NiMh with a 3.5 to 4.0Vf LED, for exemple).
Reverse polarity protection is efficient and does not reduce performance (only the current needed by the chip itself flows thru the diode. The diode Vdrop is +/-0.5V while the AMC7135 regulates down to 2.7V, so it will regulate down to 3.2V which is enough for most power LEDs)
Price is low.

Cons: These circuit boards require proper heat dissipation.
They are inefficient if the input voltage is much higher than the output(under 75% afficiency) and run hot in this case.
10% output accurency may be a problem in some cases (1000mA Imax LEDs for exemple).

Other Thoughts: I glued mines with Loctite thermal adhesive compound (one little drop on each chip cover) upside down, this provides cooling and holding. And with a little 1.5mm hole on the board, you can have all 4 wires on the same side.

Bottomline: The way they work (linear regulator) can be a problem at high input voltage (more than 5V), but in fact it is not, because with 4*1.2V NiMh you have 3.6V to 5.6V Vin.
Buying 4*AMC7135 boards can be a better choice, so you can remove some chips to have the desired current (and also some spare chips for some mods...)

Pros: Dead simple to use and they seem to work fine.

They dont get very warm while in use.
I only noticed a slight temperature increase.

Cons: I had to guess the pin out. Fortunately I guessed correctly.
The center connection is GND for both power in and the LED.
The outer ring is + for power in.
The positive terminal for the LED is on the missing IC's place and is a large round circle on the PCB.

The wires arent soldered on out of the box.
Its a trivial thing though and its easy to solder them on.

Other Thoughts: I'm powering mine from a 5v 1A switching regulator.
Someone might be interested in that.

Bottomline: I've had no problems with them.
If you have a few high powered LEDs you need to power then grab them.

Pros: -Inexpensive
-Can disable/remove 1 or 2 of the 7135s if a lower current is desired
-Thermal protection works

Cons: -one of the boards had a mis-alligned 7135 soldered on
-contact pads could be better marked

Other Thoughts: Since this was a 10-pack, I tried pushing a board to its thermal limits by running it at full load and a varying input voltage to test how far it could be pushed. The thermal shutdown kicked in, and the 7135s shut down until they cooled enough to restart. The cycle was repeated.
Thisis not recommended for an implementation method, but it's good to know the thermal regulation works.

Bottomline: A good value