I have the istick 40 tc.When you put it in TC it automatically sets itself to 40W and adjusts the Volts to hold the temp you set.In TC you need to lock in your resistance.Do this with the coil at room temp.Once the baseline resistance is locked just start low on your temp setting and work your way up till you get the vape you like...I like mine for an on the go vape,works just fine and I dont have a lot of money invested should something happen.I read alot of bad things about eleaf but mine has been flawless since day 1