Ultrafire and 18650 cells?

I'd like to buy one of the Ultrafire 2x123 flashlights, but only if I can make an 18650 cell fit. Does anybody know if the battery compartment is large enough to take one, or if it's thick enough to be bored to fit? Can anyone tell me the measurement of the battery compartment?

nope, won't fit, I have 2 ultrafires. (1 12V 4x123 type from tradedigit, and a 9V 3x123 type from ioak store on ebay).

The 17670 protected cells are a TIGHT squeez in the 4x body, soon I have 17500s coming for the shorter body, and from the looks of it, it will be equally tight.

[edit] I was just taking a closer look- there is some extra material, there might be enough to get another mm out of these with some very precision boring.. But i'm no machinist so don't take my word for it.

...I have a 2x123 cell Ultrafire and some of AWs protected 17650 cells. I tried one and it is a perfect fit. It lights up the light most of the time. I looked inside the tube and noticed that the contact behind the bezel that contacts the positive end of the battery does not protrude very far. I put one of the little magnets AW sent with the cells on the + end of the cell and it now lights it up with 100% reliability. This protected 17 mm cell is the absolute largest that could fit in the tube. The tube wall is plenty thick to allow reaming it out at least a mm larger though. The 3.7 volts this cell puts out produces a nice amount of light that is only very slightly less than what is produced using 2 123 primary cells
jc

I looked inside the tube and noticed that the contact behind the bezel that contacts the positive end of the battery does not protrude very far. I put one of the little magnets AW sent with the cells on the + end of the cell and it now lights it up with 100% reliability.

Click to expand...

I've been using the little magnets in my 4x body in the same fasion for the li-ion cells, (and between the 2 cells). 100% reliability thus far with those in place as well, just have to make sure to center the magnets well before inserting the cells and tightening down.

I know this is an older thread but I just read it. I took one of the Ultrfires 12v models and and bored it out to accomadate 2 18650 cells and ran a P91 in it, good runtime and dang bright to boot!