Harken 2631 57mm Carbo Quad Block - Swivel

Harken 57mm Quad Block — Swivel is a high-load, high-efficiency solution designed for complex control systems requiring maximum mechanical advantage. Part of the proven Carbo Air range, this quad block delivers exceptional strength, smooth performance and reliability in a compact, lightweight design.

Featuring four sheaves, this block provides maximum purchase for demanding applications where precise load control is essential. The swivel head allows the block to align naturally under changing loads, reducing friction and ensuring efficient trimming in dynamic conditions.

Built as a companion to Harken Big Boat blocks, the 57mm Carbo Air Quad Block offers impressive working loads while remaining easy to handle. Ideal for advanced mainsheet systems, cascading vangs and high-load control setups on dinghies, keelboats and small yachts.

Specifications

Length: 121 mm / 4 3/4 in

Weight: 340 g / 12 oz

Sheave Diameter: 57 mm / 2 1/4 in

Maximum Line Diameter: 10 mm / 3/8 in

Maximum Working Load: 1080 kg / 2380 lb

Breaking Load: 2270 kg / 5000 lb

Shackle Pin Diameter: 6 mm / 1/4 in

Key Features

• Quad sheave design for maximum mechanical advantage
• Low-friction Carbo Air construction for smooth, efficient performance
• High working load capacity for demanding sailing systems
• Swivel head for optimal alignment under changing loads
• Lightweight yet strong construction for performance applications
• Compact and durable design for harsh marine environments
• Ideal for advanced mainsheet systems and cascading vangs
• Suitable for dinghies, keelboats and small yachts
• Reliable performance for racing and cruising use