Specifically for use with short fill sub ohm E-Liquid.
A Nic shot is added to give non nicotine containing E-Liquids a little kick.
1 x 10ml bottle diluted into a 50ml short fill will equate to 3mg like many are used to.
2 x 10ml bottles into a large 100ml short fill makes it 3mg.
Half a 10ml bottle into small 25ml's such as Slush Wizard bring them up to 3mg.