I am rather new to vaping and I suppose I jumped the gun, buying the ProTank, I had read so much about certain e liquids ruining clearomizers. So I supposed having another battery wouldn't be such a bad idea. I'm really trying to understand the whole VV thing
dmswells - Welcome to the world of vaping and ECF, I too started with all Smokeless Image products and I want to add this is an exceptional company, with outstanding Customer Service but basically designed for the new to intermediate vaper. All of Smokeless Image products are 808 threaded. All of Smokeless Image products work flawlessly with each other unless specified only for X2 batteries. There are other vendors such as Halo and V4L that also carry 808 threaded products.
Most of Smokeless Image cartos and clearos range in the 2.4 ohm to 2.8 ohm range, the Protank or at least mine are reading about 2.5 ohm so there is not much difference from the SI products you are use to.

The above photo shows the difference in the threading for the 808 and 510. The Protank is 510 and although it can be used with an adapter on the SI X2 batteries (wasn't sure if you had just the plain X2 or the Spinner which SI also sells) there aren't any thread covers which would give it that sleek look you would get if you had a 510 threaded battery.
All the information here can be overwhelming at times, but the most improtant thing is you have found vaping!!
Hope this information helps.