57mm Harken Zircon Pulley Blocks

Harken Zircon blocks are the most advanced and highest-performing small boat blocks Harken has ever made, launched in 2023 after years of development and testing with elite sailors. The big difference from every other Harken block is what's inside: industrial ceramic ball bearings mounted in caged races, rather than the stainless steel or Delrin bearings used in the Carbo range. The cages keep the bearings properly spaced so they never bunch together and slow each other down, and the ceramic material itself is more than 700% stronger in compression than stainless bearings of the same size, meaning they stay smooth and don't deform under load. The result is a block that spins with barely any friction at all, and that responsiveness translates directly into better feel on the sheets and more precise sail control, particularly in light and shifty conditions.

Both are excellent pulley blocks, but they are designed for different sailors and different priorities. The Carbo Air range is Harken's trusted workhorse: strong, lightweight, reliable, and great value for the vast majority of dinghy and keelboat applications. The Zircon blocks are the step up from there, built specifically for sailors who want to feel every subtle shift in load and respond to it instantly. Where a 57mm Carbo Air block uses around 50 Delrin ball bearings, the equivalent Zircon uses just eight ceramic bearings in a caged race; fewer bearings, each far stronger, and none of them able to interfere with each other. The friction reduction is noticeable the moment you handle a Zircon block and the benefit is most evident in light air, where the ability to feel very slight changes in sheet load and react to them quickly can make a real difference to boat speed and sail shape.

Zircon blocks are designed for performance and racing sailors who want to squeeze every last bit of speed from their sail trim. They were developed with input from world champion sailors and first adopted ahead of the Rio Olympics for the Nacra 17 class, where the efficiency gains allowed teams to reduce their mainsheet purchase ratio while maintaining the same sail control. Since then they've been tested extensively on E Scows, A-Cats, Moths, and other high-performance classes. They work brilliantly on any system where you hand-hold lines and need to feel load changes quickly, which covers most systems on a dinghy or small keelboat, as well as light air applications and the end of cascades on larger boats. If your priority is value and durability for general sailing, the Carbo Air blocks remain a superb choice. If you race seriously and want the most responsive blocks available, Zircon is the answer.