Where to set the default with of the menutree window in the manager?

In the manager template; where do I set the default with for the tree irfame (or what else it is) window?

I have some long Pagetitles, so the treemenu gets quite wide, and therefor I have to move the rightside of the treewindow everytime I open the manager. And I often have both three and four manager windows open at the same time.

Look in the manager/frames/1.php

Right on the spot. Great. Thank you.