Ronstan RF74108A Series 75 Mast Base Block

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Ronstan RF74108A Series 75 Mast Base Block

Ronstan RF74108A Series 75 Mast Base Block. A tuned two-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. 

U.V. stabilised Acetal sheaves, Alloy cheek plates, high compression strength carbon black acetal ball bearings and a 2205 stainless steel pin for reliability and a long service life. 

Ideal for use on mainsheet, spinnaker sheet, vang, halyard and backstay applications on boats up to 14m. 


  • Class leading performance and sleek, contemporary styling.
  • Excellent dynamic and high static load performance.
  • Less than half the friction of the nearest competitor.
  • Suits attachment to 14mm (9/16”) wide mast collar post.
  • Removable 8mm (5/16”) clevis pin at head.
  • Central hub hole can be used as a becket take-off or tie-up point.
  • * Full block rated load can only be achieved with uniformly distributed load cross full length of clevis pin ie. 14mm (9/16") diameter mast collar post of 14mm (9/16")wide mast collar plate/tang.
Sheave Ø 75 mm
Max. Rope Ø 14 mm
Max. Cable Ø - mm
Pin Ø 8 mm
M.W.L. 1500* kg
B. L. 3000* kg
Weight 230 g