RF30101 Single, loop head. Precision moulded Acetal sheaves running on Acetal or Torlon® ball bearings provide high performance & low friction. The 2-stage ball bearing system provides consistent performance over the full load range. Can be fitted with a shackle in either of two planes to allow correct alignment of the block. Applications: Primary lead blocks on dinghies and catamarans and Control lines on larger yachts.