HARKEN 57 mm Aluminum Black Magic Block - Swivel, 3215

Black Magic Air blocks are a top favorite of Big Boat performance racers and cruisers. These lightweight, free-running, powerful performers are used for sail controls that see lots of action: mainsheet, runner, halyard, and spinnaker systems.
Used on offshore boats, these strong, lightweight blocks feature aluminum cheeks, and free-rolling, high-load Torlon® roller bearings for a high strength-to-weight ratio.
Use them for sail controls that see lots of action — mainsheet, runner, halyard, and spinnaker systems.

Easy MaintenanceAirBlocks are easy to clean and service.
They have few parts and no loose balls or rollers to misplace.
Unlike blocks that are riveted, fasteners allow quick disassembly with a single hex wrench.

Low Friction Caged Bearings
Roller bearings are housed in a unique center cage that keeps them separated and parallel for lower friction.
Dirt and sand fall out between the rollers.

Strong, lightweight sideplates and sheaves
6061-T6 aluminum sideplates are sculpted to remove excess weight.
Thin-profile, deep groove aluminum sheaves have radiused edges to protect high-tech lines.

Long-lasting protective finish
Sheaves and sideplates are deep-saturation Hard Lube-anodized for strength and durability

• 30% lighter, 60% higher working load than equivalent-sized ball-bearing blocks
• High- and low-load versions
• Breaking load is 2 times safe working load
• Dissimilar metals isolated to prevent corrosion - plastic isolators under all fastener heads and head posts
• Three-way head-set screw locks shackle in front or side positions, or let's block swivel to keep the line from twisting