Ultrafire 18350 1200mah 3.7v BUTTON TOP Rechargeable Lithium Battery Li-Ion UF18350
These are not protected.
I believe, though not certain, are the same length as a CR123, only wider.
Rechargeable CR123A / RCR123A 18650 & 18500 Lithium Ion Li-Ion Battery & Charger Kits Combo
If you try using CR123s in place of them, make sure the meaurements are correct, as I am only going by what I have read. You can possibly take up the slack from the smaller width of the CR123 by sleeving some cut card board from a TP or paper towel tube. I have done this in the past with good results.
Like Rick said, It would be best if you can find some protected 18350s
Good luck.