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. Black Magic blocks 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.