Here's some INFO on the "BLISS" rebuildable atty: 
Diameter: 53/64
Length: 2 7/16
FDA Approved Stainless Steel
Scientific Chemical Grade PYREX
Need I say MORE!
Diameter: 53/64
Length: 2 7/16
FDA Approved Stainless Steel
Scientific Chemical Grade PYREX
Need I say MORE!
worked when I first installed them. They were at 4.2 and 4.19 off of a Intellicharger i4 2nd gen. After turn off, I had to unscrew the cap 2 turns to get it to come back on. The fire button blinked on vape so I pulled them out, they were at 4V. I thinking they may have been loose because of the cap or the earth mag shifted. No problems after installing tip batteries. BTW I read somewhere that in a stack configuration even though they are in series the batteries discharge at different rates so they should be rotated after charging. The second battery should be put in first, first second battery put in first to keep them pair up. The lights, the power, lumbering through the menu I love this thing