At the core of Zicron performance are industrial ceramic ball bearings.
Ceramic is much harder and smoother than steel or composite, so it requires less force to start moving. Why does that matter? Through the line, you feel even the slightest pull which enables you to fine tune a sail shape. In the lightest breeze, you can ease a sheet when others can't.
The ceramic ball bearings are mounted inside caged races. The cages keep these bearings apart so they don't bunch up, touch, and stop each other. The result is a very free-running block with less energy lost to friction - in fact, the most efficient small boat block Harken's ever developed.
Give an unrigged Zicron block a strong spin, and it spins for an incredibly long time. Zicron bearings are more than 700% stronger in compression than stainless steel bearings of the same size. So, they won't deform if used within the recommended load limits.
More importantly, they don't absorb as much energy before starting to roll. This becomes evident when you need to ease a sail in very light air. You feel even the slightest fluctuations in sheet load. When used expertly, that means better sail shape and more speed.