This is a great little bubbler, and Grav does not disappoint with the helix feature... I am a sucker for that (the steamroller is love). The bowl on this is an improvement over other Grav pieces; really nice size, and the hole isn't too big. The one unfortunate thing I have noticed is that it's tough to get the water right... either there isn't enough, or if I have enough in the tank, it will bubble up occasionally and overflow into the helix/mouthpiece. I have never had this problem with a piece before, except for another Helix hammer bubbler (with a different mouthpiece attachment) that a friend has. Maybe it is just me, but it seems like something about the hammer shape makes for a not-so-perfect water/mouthpiece situation that creates leakage and some less than yummy experiences.
Again, though - most of the time, I love this piece... and it could be a personal challenge I'm having with the hammer.