Dryvit MD Spacer is a 1/8 in (3.2 mm) thick by 3 in (76 mm) wide polyethylene foam product used to create a drainage plane for the Cement Board MD System. It is applied vertically on the wall every 16 in (410 mm) on-center and at all changes in wall directions. For the Cement Board MD System, it creates a space between the air/water-resistive barrier and the cement board.