I have finally got around to trying the 306 atomizers. (took me long enough...I have a hard time with change). I am(was) a die hard 510LR dripper..... Initially, the packaging of the atomizer had me a bit perplexed. (I have used 510 atomizers exclusively for the last 2 1/2+ years.). I was thinking of it in terms of a 510 atomizer. When it arrived, I thought I had ordered a cartomizer by mistake - not realizing it is just a cover for the heating element. once I figured out the plast