A nicotine shot is an unflavoured usually high nicotine 10ml bottle that is used to add nicotine to 0mg or nicotine free short fill bottles to create a big bottle of nicotine containing e-liquid.
1 x 18mg shot in a 50ml short fill will give you 60ml of 3mg e-liquid
2 x 18mg shots in a 50ml short fill will give you 70ml of 6mg e-liquid *
2 x 18mg shots in a 100ml short fill will give you 120ml of 3mg e-liquid
* Often there is not quite enough room to make a 6mg so the user will need to use more than one bottle or add as much as they can shake the bottle and fill a tank. The remaining nicotine can be added to the short fill afterwards