18mm Moisture Resistant MR MDF (Medium Denisty Fiberboard) 2440 X 1220 X 18mm MR MDF boards are for non-load-bearing use in dry and humid conditions. Typically, MR MDF is used for skirtings, architrave, window boards and door sets for the building industry. These boards can also be used for shopfitting, hospitality and general woodworking uses. MR MDF is available with or without green dye.