something to consider - smaller mod typically means less battery capacity - so, depending on what you are vaping (in regards to wattage/ power level), may be swapping batteries/ charging frequently... personally, would suggest a removable battery mod (like the pico, as dj suggested) and an external charger (while some mods support usb charging, i don't tend to use it - personally more comfortable charging batteries on a battery charger, and considering you can get a good 2 bay charger for $20 or less, generally, the safety margin is worth it, imo - also, when mod runs down, all you have to do is swap out batteries, not wait for charge (and generally, trying to vape while charging is not great for the board/ chipset - passthrough charging is not a great feature, imo))... if you do use removable batteries, make sure you always carry spares in cases or silicone battery sleeves (do NOT care nekkid batteries - not only is it damaging to their self esteem, can cause issues if they come in contact with other metal objects in purse, bag, pocket (keys, change, pruning shears, purloined silverware, etc))