I got some dual coil clear cartos and my MV 5v modbox with a standard 3amp regulator was being flakey with them (sometimes works fine, but most times the LED lights up a second and no joy). At 3.7v (in MV modbox w/ MOSFET) the dual coils fire up but the vapor is weak. So I wanted near 5v with no regulator to muddle the performance. I liked the idea of the Puck but aesthetically, I wasn't feelin' it. So I used a 2X2 AA holder w/ 9v connector instead of two 3AA boxes. For the body, I used an empty can from Golden Layalina brand shisha (hookah tobacco), RS 3 amp switch, 510 connector, and green flat topped LED. The switch has such a heavy pressure that I don't feel it needs a master kill switch (it's not a carry in my pocket kinda thing anyway). pros: Uses 4 NiMH batteries (which I have a ton of), unregulated so it fires dual coils consistently. Warmer and fuller vapor than 3.7v but not as uncomfortably hot as 5-6v. cons: I found the NiMH batteries have a different power drop off and they drain unevenly; using a cheap RS battery meter, the closest battery to the connected + drained first leaving the other 3 with a good charge but rendering the PV done. I dunno if I'm a moderate or heavy vaper but my unscientific comparison to my MV modbox (using twin 900mah 14500s) lasting 6-8 hours is the Golden Layalina mod (using four 2500mah AAs) lasts 4 hours (performance drop after 3hrs) with my regular vaping pattern. Overall I like it, it's comfortable in my hand; I placed the LED so it's under my thumb when lit, not blasting in my eye; in a pinch I have something that can use off the shelf AAs. It was also the fastest mod I ever built (30-45 mins) minus waiting for the JB weld to cure, heh.