I'm guessing the term may refer to
tanks that can use 0.25 or lower ohm coils.
You need to check your mods specs to determine whether it can fire the coils you plan to use. Some mods might only fire down to 0.5 ohms. Others to 0.3 ohms. Some can go as low as 0.1 ohms. So if you buy a
tank that uses 0.2 ohm coils, you should buy a mod that can fire down to 0.15 or lower (taking into account factory made coils may not be exactly 0.2; they may be 0.17 or 0.22, etc).