got the other echo from DPUT today and wow...every time i take a puff on it i am so pumped the way the battery works. the first unit i got about a week ago i gave to a friend and now i finally got my own! 90 drops into the carto (didnt use a syringe, probably wouldnt even if i had one) so im guessing 3 ml if 30 drops are roughly 1 ml. if i take a drip tip off the echo, the unit is just as long as the ego 900mh battery with a drip tip.im suspecting that i will use close to 2 carto fills/day. ah this thing is nice!!