Sails, Shape, Size and Design How do I select the right furling system for my boat?The Ordering Furling Guide explains how to choose a furling unit and accessories for your boat. You will need to know the clevis pin diameter as well as your headstay length and diameter. What are the differences between Harken's MKIV and MKIV Ocean furlers?Both are designed for longevity and ease of use, but the MKIV has additional features that make it more suitable for performance cruising and racing.   MKIV MKIV Ocean Foils Aerodynamic foil profile. Double grooves for faster hoists, douses, and sail changes. Single groove, round profile for easy rolling.Pass headstay wire and marine eye through foils. Cut top foil to fit. Bottom foil adjusts to fine-tune unit length. Halyard and Tack Swivels Independent swivels for improved sail shape. Fixed swivel. Drum Split drum removes for racing. One-piece fixed drum, spool, and guard. Line  Line is included. Line is not included. Are all Harken jib Reefing and furling systems capable of reefing a headsail?Yes, as long as the furling system has aluminum extrusions covering the headstay.Can I change sails with my Harken jib reefing and furling system?Yes, changing headsails is simple. Just attach the head and tack to their shackles, pass the luff tape through the prefeeder and feeder, and hoist. The feeders smooth out wrinkles and minor twists in the sail so you can easily raise sail while at the mast or in the cockpit. Choose the optional snap shackles if you plan to make a lot of sail changes. How can I reduce heel and get better control with a reefed sail?Harken's MKIV Jib reefing and furling units solve the inefficient shape of reefed sails with independent head and tack swivels. The independent swivels allow the middle to furl first, flattening the sail and reducing heel.For the best results, use a sail designed specifically for reefing with your MKIV furler. Reefing sails should be designed to have good shape from about