Thanks for the earlier responses about the Cig2O. The info on LeCig's Web site was especially helpful - their customer service said that the Cig2O is a D-1. There's also a video on their site that describes the difference between the D-1 and the D-2 (basically the connection is a little longer on the D-2) and mine does appear to be a D-1 based on just looking at the proportions. But does anyone have figures on the length just to make sure before I place an order for another brand of cartomizer to be sure they will fit?