The following ball bearing air blocks:• 2-1/2" diameter sheaves with a 2800 pound working load suitable for line up to 1/2"
     2) single blocks
     1) double block
     2) stand up blocks with deck plate
• 3" diameter sheaves with a 4000 pound working load suitable for line up to 5/8"
     1) single block used for the aft mounted boom block where a single sheave and shackle must carry the same load that is shared by two shackles and sheaves elsewhere.

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.

1) These blocks are far more robust than those used on earlier boats. The double block that mounts on the traveler will not fit the small car on the early arched NICRO traveler unless you jury-rig multiple shackles as an interface between the traveler car and the block's beefy shackle.

2) Due to the weight and value of this kit, it does not conform to our standard shipping policies. Call 800-959-7245 (800-959-SAIL) for a shipping estimate.