One sheet of ferrous paperboard of 20/25 cm.
One magnetic sheet of 20 / 25cm and 2 mm width.
One magnetic sheet of 20 / 25cm and 2 mm width, and one sheet of ferrous paperboard witht the same dimensions.
Three magnetic sheet of 20 / 25cm and 2 mm width, and three sheet of ferrous paperboard witht the same dimensions.