Ronstan Series 20 Ball Bearing Block - Single - Exit Cover Plate - RF20711Series 20 Ball Bearing Block Single Exit Cover Plate Features: Precision molded Acetal sheaves running on stainless steel or Torlon ball bearings provide high performance & low friction Applications: Exit blocks minimise friction in lines passing through the deck or exiting masts and booms Materials: UV Stabilized Acetal sheave Grade 316 stainless steel load strap and head fitting Specifications: Sheave : 20mm(3 4") Max. Rope : 6mm(1 4") Pin: 4mm(5