The following ball bearing air blocks:
• 3-1/4" diameter sheaves with a 3500 pound working load suitable for line up to 5/8"
     3) single blocks
     1) double block
     1) single block with becket

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 double blocks, tighten the set screw (single blocks) or nut (double 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.