Ronstan Series 40 Double Full-Swivel Sailing Block

The Ronstan Series 40 Double Full-Swivel Sailing Block is a rugged two-sheave block for mainsheets, halyards, vangs, and spinnaker controls on dinghies and small sportboats. Its full-swivel head lets the block rotate with the tackle, reducing the tendency for the rope to scrub a cheek when the load direction changes. Two sheaves provide a compact way to add mechanical advantage without hanging separate single blocks from the same attachment point. The all-purpose Series 40 construction favors long service life and straightforward maintenance for boats that are sailed regularly.

UV-stabilized Acetal sheaves are self-lubricating, so the block does not depend on a delicate exposed bearing surface for everyday operation. Fiber-reinforced nylon cheeks resist impact and weather, while the primary load hardware is stainless steel for marine corrosion resistance. A slotted-pin shackle is designed to reduce the chance of a loose pin or fouled line around the attachment. This construction makes the block equally sensible for club racing, training boats, and cruising dinghies that spend plenty of time wet.

• Double-sheave layout for compact purchase systems
• Full-swivel head follows changing line direction
• Self-lubricating Acetal sheaves
• Slotted-pin shackle helps keep the attachment tidy

This model accepts line up to 10mm (7/16 in), with a published maximum working load of 1,320 lb and a 2,650 lb breaking load. At about 4.8 oz, it remains light enough for moving tackle while offering substantial reserve strength. Install it where the swivel can rotate freely and where both rope runs enter the sheaves without a hard cross-lead. For more Series 40 blocks and small-boat rigging parts, browse more Sailing Hardware.