Harken’s integral hydraulic backstay adjuster provides the power to optimize sail shape quickly for racers and adjust mast tension for smoother furling for cruisers. The cylinder features a built-in, single-acting pump. Every unit includes a hardcoat-anodized aluminum cylinder and pump, valve, and stainless pump handle with two attachment options: 1) a roll pin, that when installed, locks the handle permanently, 2) the roll pin can be left off and the handle may be inserted when needed, but stored separately. Cylinders include a clevis pin on both ends. A fiberglass position indicator attached to the top clevis pin slides down the cylinder as it’s retracted for repeatable tension settings. Standard eye-jaw toggles fit all Harken cylinders and are recommended on all installations. The pressure-release knob turns clockwise to close and pump, counterclockwise to release. When closing the pump, the knob cannot be over-tightened by hand, preventing damage to the valve. Release speed depends on how far open the knob is turned. Pressure relief is factory set to prevent crew from over-tensioning the backstay. Harken integral backstay adjusters come in four sizes to fit boats 9 - 18 m (30 - 60') with stay diameters of 5 - 10 mm (7/32 - 3/8").