Here's a link to a pdf giving, amongst other things, the hose size for the thermobob 3.
http://www.watt-man.com/uploads/What...ent_Thermo.pdf
It says that there is a 5/8 inch and 3/4 inch available.
1/ what's this " old money "stuff, where's the metric
2/ I've no idea what the internal diameter of our hoses are
