I know it's kind of an old thread, but I had put my NovaTac 120P aside in favor of a ZL SC600 as my EDC, mainly because I love having hours and hours of light provided by the 18650, but now, after spending a whopping $8 to convert it to 18650 ($6 for the tube from Lighthound including shipping + $2 for the brass piece from ACE), I've got my NovaTac 120P back as my main light again (also sporting a new Nichia HiCRI 219 4500k LED).
Thanks, Hogokansatsukan, for taking the time to document and share this EASY mod. Highly recommended!
Wow, I REALLY hate necroposts, but I have to give credit where credit is due. Thanks to Hogokansatsukan for this great post! Fortunately the pics are still up. I had bought the extended tube for my Novatac SP120 years ago, I think from Lighthound. I could never get it to work, and then I lost the spring. For some reason I hung on to the tube. I decided to invest in the brass strip, which I couldn't find online for less than $8. But now I'm using the tube, and with 18650s! Woohoo!!