If you want more tanks, I'd recommend getting a different rba tank system and expand one's collection. Would look at the flash-e-vapor, Rose2, Taifun GT, and if you really want to rock your vape world, ain't nothing better than the Gus Estia 510 rba tank system, tri-coiled, juice and air control, just don't get any better.!!!
In my opinion, an Authentic rba is always the better value, though some clones come dang close, but the Russian/Kayfun is like over a year old design and hasn't seen any real improvements on the original design. All the rba's I've mentioned will out vape it, depending on ones skill's and experience.
Personally, would highly recommend checking out the flash-e-vapor V2 or 3. On of me most favorite rba tank systems yet devised. Excellent vape, easy to build, can work on build with a full tank of juice, and can be used in both dripper and tanked mode. A must have for any vapers collection.
The Russian was me first rba of the collection, and is still used in rotation, but it's in the back of the pack, far as top performers goes. Just so many newer innovative tank systems to be had, that will seriously improve ones vape potential.. of course, it's all contingent on ones building + wicking skills, and quality of gear.
Vape long and Prosper.!!!!