i had my first grav bong the other day...i was alreaddy stoned off my face, my mates, mate made one, i was trippin out when he showed me how it worked...then i tried it...and FUCK it sent me right off...it hit me like nothin else. i had TWO cones and i couldnt hav another...i could still feltl the smoke trapped in my lungs. but congrats to the smart bastard that invented them!