Harken's 2 1/4" Upright Lead Block is used for main and jib sheets on course racing keelboats, scows and dinghies with large mains. Often used for spinnaker halyards and sheets on small offshore boats. 57mm sheave. Delrin ball bearings. 7/16" line diameter. Cheek is made from plastic and stainless steel. Requires #8 fasteners (sold separately). 5.5oz.