Ronstan Series 40 Quad Swivel Orbit Block

The Ronstan Series 40 Quad Swivel Orbit Block packages four ball-bearing sheaves into one compact moving block for higher-ratio mainsheet and control systems. A swiveling shackle lets the assembly follow the purchase as the load angle changes, helping all four rope runs remain aligned. Ronstan's Series 40 Orbit family is intended for performance dinghies, catamarans, and sportsboats where low friction and low moving weight matter. The quad format is especially useful when substantial mechanical advantage is needed without spreading several smaller blocks around the same attachment point.

Each sheave uses a two-stage bearing system that combines ball bearings with secondary full-contact support for heavier loads. Toughened glass-fiber reinforced nylon cheeks keep the structure light while replacing the metal straps common on older utility blocks. The swivel head allows the block to rotate with the purchase, reducing side loading when the tackle changes direction. Keeping four sheaves in one housing also makes the finished system easier to rig and inspect.

• Four-sheave Orbit configuration for higher-ratio tackles
• Swivel shackle for changing load angles
• Two-stage low-friction bearing system
• Lightweight reinforced composite cheeks

Ronstan specifies line up to 3/8 in, a maximum working load of 1,320 lb, and a 2,650 lb breaking load. The published weight is about 6.8 oz, which helps keep a large moving purchase from becoming unnecessarily heavy. Lay out the reeving carefully so none of the four rope runs cross or pull a sheave sideways. For more quad blocks and high-ratio sail-control hardware, browse more Sailing Hardware.