Make quick backstay adjustments using the power of hydraulics. Harken Hydraulic Backstay Adjusters give sailors the power to tension the backstay and optimize sail shape quickly. An integrated, double-action pump delivers oil on push and pull strokes of the lever and is twice as fast as single action pumps; backstay adjustments are quick so that you can return your focus on maintaining the optimum course.Pressure release knob turns easily to control pressure. Clockwise to close the valve and allow the pump to tension the backstay and counterclockwise to release tension. To prevent damaging the valve, the knob cannot be over-tightened by hand. Pressure release rates (speed) is dependent on how far open the knob is turned. Pressure relief of the cylinder is factory set to prevent crew from over-tensioning the backstay.An analog gauge provides incremental readings 0-5 (0-5000 psi) and is mounted at the top of the cylinder for easy inspection. Four position adjustment makes for easy viewing from the cockpit.Backstay assemblies includea hardcoat-anodized aluminum cylinder body to resist corrosion, a valve pressure control knob, an analog gauge, and stainless steel pump handle. The handle has three attachment options: permanently installed with a pin; semi-permanently with an O-ring to secure the handle in socket; temporarily without O-ring and roll pin. All pins and plugs are stainless steel. Clevis pins are installed on both ends of the cylinder and fit standard eye-jaw toggle. Four sizes are available to fit boats with 5 to 10mm (7/32" to 3/8") wire, or boats approximately 30' to 60' in length. Key Features Provides high load backstay adjustment with less effort Integrated double acting pump transfers oil twice as fast for quick adjustments Handle has three installation options Analog gauge with 4 position adjustment provides reference for backstay tension Pressure release knob cannot be over tightened to protect the valve from damage Speed of pressure release can be controlled Pressure release valve prevents over tensioning the backstay Includes clevis pins for eye-jaw toggles Available in 4 sizes to fit a variety of boats from 30'—60' (with 7/32" to 3/8" backstay wire)