North 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 finest adjustment with ease. The extension ring has a simple to use Pop & Slide system, so setting the right length becomes intuitive. The U-Pin button sits discreetly on the extension tube and has a manual locking function for safety and peace of mind, during long slalom reaches or ocean runs. High-grade plastic and stainless steel components ensure the extension will be in your quiver for many years to come.