Your probably right on the 1/2". I'm relying on my ever failing memory. [
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Fiberglass tape is nothing more than fiberglass cloth cut into strips. The only advantage it has versus cutting your own strips from cloth is that the edges are straight so it doesn't have as much of a tendency to un-ravel like a piece of cut cloth can.
[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXK255&P=0]Fiberglass Tape[/link]