North Sails MDM extensions ensure that you spend less time rigging and maximize your time out on the water. 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.