6.5mm would not use it for anything over 5 gallon batches(19L)
With tubing but no clamps
€25 ono
(http://i.imgur.com/q2o2Ioml.jpg)
Where are you based ?
Dublin, tis also handy for a double chill ie passing tap water through this sitting in an ice cold bucket of water then onto the bigger chiller
interested - what diameter?
17cm