Review: iSub Apex by Innokin

Innokin, long known for their quality vaping hardware, has released their first top-fill tank. The iSub Apex is a 100% Stainless Steel tank with a 3ml reservoir for juice with both top and bottom airflow slots.

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I’m on a quest to find the perfect top-fill tank, and when I first heard about the iSub Apex from Innokin, I was hoping I finally found it. With it’s unique airflow slots, “Quick & Clean Top-Fill” holes, and it’s small form factor, I was expecting a lot. Unfortunately, for me, this tank fell short of what I was hoping for.

Available Coils

Innokin is making things easy for past iSub owners. The Apex uses the same coils that are available for the original iSub and iSub G. That means if you are upgrading from one of their past tanks, you are already good to go.

There are currently 3 options for coils. Two sub-ohm versions, 0.2 ohms and 0.5 ohms as well as a standard 2.0 ohm coil.

All three coils are your standard kanthal wire. The tank itself comes with 2x .5 ohm coils, and if you’re like me, you are going to need it (more info on why later in this review).

There are also rumors of a RBA deck becoming available for the iSub series, but at the time of writing this article, none is available, and my Innokin rep couldn’t provide any further info.

There are no options for Nickel or Titanium, so use of this tank with a temperature controlled mod will be very limited.

Resistance Rated Wattage
0.2 Ohms 35-50w
0.5 Ohms 20-35w
2.0 ohms 8-12w



The iSub Apex has a couple unique features not currently available un other tanks. The biggest one in my opinion is its airflow design.

Airflow Open

Even though the “bottom” airflow slots are above the tank, they actually pull the air through the bottom of the tank. This gives you two huge advantages.

First, because the airflow is pulled from above the tank, then down the sides of the tank and back up through the heating element, it keeps the tank cool to the touch. That means rarely, after chain vaping, will you ever feel your tank heat up. The more you vape on it, the more cool air is pulled through the tank, cooling it down. This actually works surprisingly well. For the couple weeks I used this tank, I never felt it hot, or even warm, to the touch.

Airflow Closed

Secondly (and this is pretty big in my opinion), due to the intake being above the tank, you’ll get zero leaking. I said that right, this is the first tank that I’ve ever owned that just didn’t leak. Sure there is some places on the tank juice can leak out, but that’s generally from overfilling (which is a problem). Never again will you go to grab your mod, and end up with juice all over your hand.

The next is their top-fill design, which they call “Quick & Clean Top-Fill”. While definitely quick, I’m not sure if I’d consider it “clean”. Instead of having to remove the drip tip like the Triton, you only need to twist the top to open the fill holes. While being a convenient, I ended up getting messier than with a normal non-top-fill tank. Since the top fill holes are recessed and always exposed, it creates a major issue with the design.

Fill Holes Open

Fill Holes Open

It’s near impossible to fill this tank without getting juice on the top. What makes it worse is, since the fill holes are recessed into the top, it’s very difficult to actually wipe away excess juice. That also means you’ll usually end up with juice in and around the areas where you fill the tank (which is exposed). Then when you twist the top to close it, the problem just gets compounded because the juice gets spread around the underside of the top. Next time you open it back up, even if you managed to wipe it clean, the juice will just get spread around again. To add to that, since the top is going to be consistently wet, it will attract dirt and other stuff pretty easily. On numerous occasions I pulled the tank out of my pocket only to find lint and other stuff stuck to the top.

The tank is also listed as a 3ml capacity, but I found when filling it to the very top, it can (and will) leak out of the top ring used to open and close the fill holes. Because of that, I’d say this tank has effectively a 2.5ml capacity.


While there is plenty of good about this tank, I found myself switching back to the Triton after only about two weeks of using this.

Besides the issues I’ve already mentioned, there’s one major issue I just can’t get around. Because of the fancy airflow that pulls the air from the top of the tank, then down the sides, and back up through the heating element, most of the tank is covered.

IMG_2693Trying to figure out how much juice is left in the tank, or even how much you filled it is pretty hard to do. Within two days of using this tank, I completely burned my first coil due to dry hits. Unless you are REALLY conscious about how much juice is left in the tank (and I thought I was), it’s extremely easy to not realize you’re empty. Even after switching to the second coil, and trying to pay close attention to how much juice was in the tank, I still did it a couple times.

On top of that, it makes filling the tank kind of a pain. Because the window into the tank is so small, after the tank is half way full, it becomes hard to judge how much room is left for juice. You kind of have to look through the fill hole to see how high the juice level is. There was also plenty of times when using clear juices that it was just impossible to tell if the tank was full or empty without shaking it and seeing if bubbles form.

So the question is, would I recommend this tank to other people? Unfortunately, the answer to that is probably not. While on paper, it works really well, the annoyance factor is just too high. Having to constantly worry about how much juice is in the tank, and whether there’s juice still sitting on the top is just not worth it when there are other similar priced tanks on the market that you can use.

That said, if the obstructed tank, and exposed fill holes don’t bother you, or you are sitting on a ton of iSub coils, you may be happy with this tank.

Author: John

I've always been a huge tech junky. If there's a battery and some kind of silicon, I love tinkering with it. When it comes to my vapes, I prefer the hands off approach for my every day device. A nice tank, pre-made coil, and mod with battery built in is just too convenient. One day I'll build a coil. One day.

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