Harken soft-attach Fly blocks are designed to provide strength beyond mass, providing big power in a low-aero package. Designed specifically for high-tech line, these efficient blocks have an incredible working load for their small size. 18 mm blocks feature an integrated stainless-steel inner race and rivet, stainless steel ball bearings, and composite fiber-reinforced sideplates. Triples feature composite line guides that are integrated into the block head. They keep the block aligned correctly by pushing the lashing line to the outer edges of the block's head. High-Performance Fishing Tool: The triple is gaining traction as a high-performance sport fishing tool, generally placed on the “inside end” of the outrigger guiding halyards for trolling. A length of Spectra line is included. Spectra is a registered trademark of Honeywell International, Inc.