Nhaler has 510 mega cartos which is the same diameter as a regular 510 battery (or mega battery) but not the eGo battery. The carto is a bit longer than most cartomizers, hence 'mega'. They are a tad larger in diameter than the atomizer and that makes the cone of the eGo too tight. I got a few extra cones and used a taper die to ream them out so the gap is the same as with an atomizer. OR you can just not use the cone with the cartomizer. Also drip tips are nice with this carto (or another carto with a better ohm rating. This one (mega) is 3.4 which is weak for an eGo batt). Try Provapes for their LR cartomizers for the 510.
The NEW mega
eGo cartomizers are much different. They are the diameter of an eGo battery. Don't think Drew has them yet at nhaler but they can be had a cignot, heaven gifts, Totally Wicked and likely Janty if they're in stock. Here's cignot:
eGo cartomizer
You don't use the cone for these and actually the new mega eGo atomizer and cartridge are the same size and easier to refill:
eGo cylinder mega atomizer
eGo cylinder mega cartridge
pics here (thanks Katya):
Janty World - Review of the big eGo atomizer & cart - Janty World | Janty World