Holt Allen's Dual Arm Jammer features a second cleat for lines led vertically through the base of its revolutionary swivel base. Mainsheet trimmers will appreciate how the second cam enables vang or the backstay control in the same swivel base that handles the mainsheet. The lightweight wire frame provides the perfect height, angle, and torsional rigidity. The swivel base incorporates a dual ball race for maximum efficiency and has optional click stops to limit the swivel rotation. The arc of the swing to prevent the arm from falling to leeward when the sheet is not loaded is set by adjustable base pins. Fireball and Etchells sailors the world over use this combo base, arms, and cleats with the appropriate block of their choice. The swivel base has a four-hole pattern with 20mm spacing on centers. Use M5 3/16 in. (5mm) fasteners.