Using ball bearings, Bullet blocks to lead lines with a minimum of friction. A wide range of variations let these versatile blocks adapt to almost all control line situations. Wire Bullet Blocks use roller bearings, which carry higher loads than ball bearings, and feature Teflon impregnated, Hardkote-anodized aluminum sheaves. Use for halyards and other small boat wire controls. The 359 is a dounhaul/cunningham assembly for catamarans and the base for an 4:1 double-ended system. Common features include: Sheave; 1-1/8", Max.Line; 5/16", Breaking Strength; 2000lbs.