Use the 40 mm Black Magic Carbo AirBlock for jib and mainsheet systems on high performance dinghies. For the ultimate system, use Technora, Dyneem, Kevlar, or Spectra line with cover stripped where it runs through the blocks; however, the 40mm Carbo Blocks witll take line up to 3/8-inch (10mm). These blocks are also ideal for highly loaded control lines on small keelboats. The double and triple can lock in two directions or swivel freely. Use for: Main/jib sheets, Sheets, Control lines. Sheave: 1 9/16-inch 40mm Length: 3 3/8-inch 86mm Weight with shackle: 1.6oz 44grams Shackle pin: 5/32-inch 4mm Max line: 3/8-inch 10mm Safe working load: 485lbs 220kgs Breaking strength: 1620lbs 735kgs