0.7 Ohm Option

These are designed for the Nautilus 2 tank.  They give a much stronger vape compared to the previous 1.6.

1.6 & 1.8 Option

These are designed to be used across the whole range of Nautilus and K3 tanks.

From using all 3 coils I have found the following however this is only my opinion and you might find different outcomes as all vaper's use different liquids, battery wattage and inhaling patterns:

0.7 are nice when a wholesome vape is required.  I tend to use these as direct lung at times and mouth to lung when using higher nicotine content.  I use these at 18 watts and reduce it to 14 when using higher nicotine content normally over 6mg.  However everyone vapes differently and over time have found other users using settings that I would never use.

1.6 is a nice in between range.  It gives me a decent mouth to lung vape.  Due to a decent build quality of the juice holes I always get a nice fully cotton soaked vape allowing decent flavor to pull through unlike the 0.7 I feel is unable to handle binge inhaling.

1.8 are a notch lower in vape compared to the 1.6's.  The 1.8's are meant to increase battery and coil life and I have noticed only a slight difference between the two.  Most customer feedback is they are about the same and some state the 1.8s are defiantly more convenient due to the life span of battery and coil.  

I use 1.6 and 1.8 ohm coils locked on 10 watts however some like to use these ranging from 7.5 to 12.5 watts.  I always use 50VG 50PG liquid and have tried the 70VG 30PG liquid which for me was still vapable however if you chain vape you will notice dry hits.