The Harken 29 mm Zircon Block, part number 2185, has a maximum working load of 80 kg or 175 lbs. It also has a maximum line Ø of 6 mm or 1/4 in and sheave Ø of 29 mm or 1 1/8 in. The newest Zircon models, with 29 mm sheave diameters, expand the current offering from eight to eighteen models. While Zircon is not a universally applicable option, these smaller sizes make it suitable for control lines that require multi-part purchases. Additionally, Zircon is highly responsive to adjustments, allowing for immediate reaction when easing pressure on the Cunningham or jib leads for added power in choppy conditions.