Harken's 57mm Black Magic AirBlocks are the work horses of the entire Harken line of blocks. Used on small boats and big boats, hey are used for sail controls that see lots of action such as mainsheet, runner, halyard, and spinnaker systems.
They feature strong and long-lasting Torlon roller bearings housed in a center cage with sculpted hardcoat-anodized aluminum sideplates to protect the sideload ball bearings. Easily adaptable, they feature a three-way head system and come in high-and low-load configurations. The low-load AirBlocks can be identified by their red isolators and come with 316 stainless steel shackles. Otherwise, they are the same as their high-load counterparts in every other way.
Corrosion is minimized by isolating dissimilar metals. AirBlocks can be taken apart with a single hex wrench.