Cartotanks come in two sizes, or rather two lengths to be more accurate, when determining which cartomizer to use with them. The following graphic might help your confusion.

To further explain, the shorter or standard length tanks will require a Boge carto. Smoktech doesn't make a shorter tank replacement carto.
The longer length tanks will require either a Boge XL or Smoktech.
I recommend you read my blog for articles that I have written about cartomizers and tanks. They can be easily accessed by clicking the link below my avatar, and then clicking the title of the article you wish to read.
One has a detailed description, with video, on cartotanks. Another one has a list of vendors that sell the laser-drilled cartomizers used in cartotanks.