These are high quality stainless steel blocks with aluminum sheaves. The open design is lightweight. It also creates a large diameter race so there are more bearings to divide the load. They will run free in heavy air or light.

To prevent the line from twisting or binding when used in a cascade or mainsheet system the blocks in this kit are supplied with a feature to lock the rotation of the shackle that is on top of the body of the block. With the use of an Allen wrench for the single blocks and an open ended wrench for the triple blocks, tighten the set screw (single blocks) or nut (triple blocks) to lock the shackle in position. When used as a swiveling block, ensure the set screw or nut is not tightened and the swiveling shackle can self-align to find the fairest lead.