I have a Volt and from LiteCigUSA.net I use the PLAIN clear colored plastic 510/901/KR808D-1 drip tips (with swirled colored plastic ones are a bit too tight) and I use the plain rounded black delrin 510/901/KR808D-1 (I do not know if the flat tip would fit). I recommend buying a couple of the colored ones. Out of the 7 I have bought one was once too tight (and he sent me a replacement).
I do not recommend dripping into the top - the
juice would aim right for the air channel. But the drip tip as a mouthpiece pulls out easily making it easy to check the stuffing or add juice.