These have a 2 ml capacity, flat tip and replaceable, bottom 1.8 ohm dual coil which is just right for your 3.7 volt battery. We also have replacable tanks if yours breaks.
I really like these for an inexpensive but coil replaceable clearomizer. Coil is 1.8 ohm and really has tons of vapor and taste. We have been through many types but we like this one.