What space is needed between two door panels to install an Endura Astragal System?

You will need a gap of 27/32" between the door panels.

The body of the Endura Ultimate Astragal Systems extends 11/16" off of the edge of the inactive door panel. The ideal margin between the face of the astragal system and the edge of the active door panel is 5/32". Therefore, you need a space of 27/32" between the active and inactive door panels.

The astragal body is designed to fit around a door panel that is 1-3/4" or 1-11/16" thick.