I agree with everything baditude posted.
I myself didnt have the money to spend so i started with smok dct tanks, they are glass and cheap at
www.desertvapes.com
Fast tech has the same ones for less than $7 but plan on a 4 week wait time.
I get my cartomizera from ibtanked. They are flanged and are easy to use. I have never had a doa from them or had any burnt taste or wicking issues.
I currently own 8 6ml smok dct tanks, 4 from desert vapes, 4 from fast tech. I own 3 smaller glass smok dct tanks also found at desert vapes. Two smaller dct plastic tanks from fast tech..... And two ibtanks.
Important note is the ibtank glass is cheap to replace should it break, about $5.
I think that the smok dct tanks are easier to take on and off the battery. The flanged part of the carto kinda locks into place so when you turn your tank it will unscrew easily, a lot of times my ibtank will just turn and turn, but will not unscrew, it just spins around the cartomizer. So much so that i now buy my cartomizers the next size up than the tank i am installing it into.
I like both equally. Ibtank has great selection in sizes. They are superior in quality.
I highly reccomend any carto user to buy one.
But if you just want to buy one to try, go with smok glass dct tank big or small from
www.desertvapes.com they work just the same. Will run you about $10 with shipping, maybe a few bucks more if you get your cartomizers from them as well.