I have no idea if any such product exists, but I'm looking for something to extend the length of the 306 atty. So, it would have the 510 male threads at one end (to connect to the battery), and 510 female threads on the other end, (to connect to the 510/306). I've gotten used to the length of the 510, and using a 306 just seems too close to the battery now. Plus, you can't use a 306 with the cone on the Ego without some sort of extender. For the time being, I've been using a 510/901 adapter, into a 901/510 connector, but I would prefer a one-piece. Does this exist? Thanks.