I really enjoy these, and the 510 XXXL version.
They are exactly the same less the cone shroud on the eGo version.
I find they both hold exactly the same ... about 3.5 ml.
And an eGo type B mega drip tip fits. Its a must IMO if you plan on using these.
The rubber nipple collects lint, and is freakin huge.
While they are great at 3.X volts they really rock at 5v
Good review.