Harken 2637 40mm Carbo Air Single Block with Swivel and Becket

The Harken 2637 Carbo Air® 40mm Single Block with Swivel and Becket is a compact, high-performance sailing block engineered for low-friction line control and reliable sail trimming. Part of Harken's popular Carbo Air® series, this block delivers outstanding strength-to-weight performance at an accessible price point.

Built from tough fiber-reinforced composite, the Carbo Air design is 30% lighter and offers a 60% higher working load than traditional Classic blocks. The open-air construction eliminates unnecessary material, while densely packed glass fibers in the nylon resin sideplates provide exceptional structural strength without the added weight of stainless steel straps.

Key Features:

• Sheave diameter: 40mm (1-9/16 in.)
• Overall length: 102mm (4 in.)
• Maximum line diameter: 10mm (3/8 in.)
• Maximum working load: 220 kg (485 lb.)
• Breaking load: 735 kg (1,620 lb.)
• Shackle pin diameter: 4mm (5/32 in.)
• Weight: 48g (1.7 oz.)
• Patented switch locks shackle in front or side position, or allows block to swivel freely to prevent line twist
• Ball bearings, sheave, and sideplates are UV-stabilized with carbon black for long-term weather protection
• Becket provides a convenient attachment point for additional lines or blocks in multi-purchase systems
• Free-running ball bearings roll on curved races for efficient load distribution

The Harken 2637 is ideal for main sheets, jib sheets, spinnaker sheets, and control lines on dinghies, sportboats, and larger keelboats. Its compact profile and high working load make it a versatile choice for a wide range of one-design and cruising applications.