its 14mm there are 4 holes on the bottom of the skull. its pretty nice i got a deal on it i paid 60 it was priced 100.., and it comes with a bubbler hook up. its kind cool i like skulls so i had to get it.. the dark blue is kinda nice too heres my milk shot, [ame="http://tinypic.com/player.php?v=zixbo9&s=5"]View My Video[/ame]
I got the same one here in Miami, paid 80 for it and the skull is green instead of blue. I love the versatility of using it as an ac or just straight up as a bubb