The fixed outer frame and the moving inner frame are made of aluminum material resistant to bending and buckling. Fire Wicks Graphite, Drywall A1 boardex. YDK Series control flaps, the Fire Resistant Shaft Cover provide all the functionality, as well as keeping the fire area at minimum level for 90 minutes and allowing people to escape to safe zones. The outer frame is applied as a standard by screwing on the gypsum board.