... 4F& API 8C mandates. Crown blockForged with hight strength steel, the grooved sheaves are hardened bu medium frequency induction to provide extended ... prevent the wire rope from running out of sheaves. Each crown block conforms to API 4F & API 8C mandates. Model TC135TC225TC315TC450Max ... (11,700)7,400(16,300)9,500(20,940) crown block