We have tested other Clearomizers and nothing compare to iSub Tank. They do not leak, no burning taste, are easy to refill with e-Liquid .They are not a throw away clearomizer, you simply replace coil. Because we keep the coils at a low cost, we always advice our customers to change the coil frequently to have a more enjoyable experience. Please Note: You fill the clearomizer from the top and change the coil from the bottom. To replace the coil. you unscrew the old coil and twist the new one on tightly.