North WS MDM Aluminium ExtensionNorth Sails MDM extensions ensure that you spend less time rigging and maximize your time out on the water. The Aluminium is our alternative to the Carbon, with the same innovative features. The MDM extension includes 4 oversized, low friction, easy thread, corrosion resistant plastic pulleys, that line up perfectly with the sail. When combined with the low stretch Dyneema rope, an 8 to 1 pulley ratio makes high tension downhaul easier, allowing the