It is spring loaded, but the iStick came with an adapter for the e-go tanks (I think that's what it's for?) and it worked just fine, albeit a bit silly looking. When comparing the Herakles to my Cthulhu, I can see very clearly the pin is a few thousandths shorter on the Herakles than the Cthulhu, even when the Cthulhu is threaded all the way in. For the sake of convenience, I'll go with this until setup I trip over a better solution.