57 mm Aluminum Black Magic Double Block - Sheave Control

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 Maintenance —
AirBlocks 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 falls 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 headposts
• Three-way head - set screw locks shackle in front or side positions, or lets block swivel to keep line from twisting