Surefoot, Fluval do these valves.
Sorry about the piccie guys, but this was for an article I did.
They are actually a double valve that seperates. There is only about a teaspoon of liquid between the valves. They do them in 16mm sizes as well.
[ 10-19-2001: Message edited by: Darkhorse ]
[ 10-19-2001: Message edited by: Darkhorse ]