10ml bottles are the most popular way of buying e-liquid, generally they are a 50 / 50 mix of PG and VG (unless stated otherwise). Due to the current TPD laws in the UK, you can only buy liquid pre-mixed with nicotine in 10ml bottles.
You’ll notice that there are two types of E-Liquid that come in 10ml bottles, ‘Nic Salts’ and ‘Freebase’. Both are essentially made the same way with the same ingredients (PG / VG, Flavourings), but the key difference is how the nicotine is added to the liquid and how it is delivered to your body. Neither one is better than the other, it all depends on your needs.
Freebase nicotine is available in various strengths, most commonly 3mg, 6mg, 12mg and 18mg.
Nic salts are predominantly available in NS 10mg and NS 20mg. There are a few exceptions who make a NS 5mg.
There are also other ‘hybrid’ liquids that use a mixture of Nic salts and standard nicotine, such as ‘Ohm Brew’, and these are available in NS 3mg, NS 6mg, NS 12mg and NS 18mg.
Put simply, freebase liquid uses nicotine in its purest chemical form, which is then mixed and distilled into a mix of PG and VG (as well as other flavourings). Whereas for nic salts, the nicotine is extracted directly from the tobacco leaf itself. Chemically, nic salts alter the Ph level of the liquid, which makes it smoother to inhale, reducing the throat hit you experience. Nic salts can also absorb into your bloodstream much faster, when compared to standard ‘Freebase’ nicotine.
In summary, freebase liquid tends to be harsher the higher in nicotine strength you go. A Nic Salt will allow you to achieve the higher strengths of nicotine without the harsh throat hit. As well as being smoother on your throat, Nicotine Salts are faster acting, offering the “nicotine rush” you’d typically associate with the first cigarette of the day.
The key thing to remember is that because of the mixture of PG/VG in salts and the higher nicotine content, you will need to use them in lower powered MTL kits with a coil resistance at a minimum of 0.6ohm.