What is the proper name of the METAL cross bars installed between the panes of thermo-pane windows, muttons, muntons, mullions or grillwork?

Can u give us a picture?

Chuck

Grilles if they are snap ins on the inside, mullins if they are between the panes. However, these terms have been so misused over the years it no longer matters and many makes use them all. Big Blue Window? Window grilles, grille, mullion, muntins, mullions, muntin, grills, & grids (http://www.bigbluewindow.com/)