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Ronstan 70 mm Series 70 Orbit Block

  • Cheek Block
  • Safe Working Load: 1540 lbs
  • Maximum Line Size: 1/2"
  • Item #: 
    Model #: 


    Shipping Weight: 
    0.30 Lbs.
    List Price: 
    Status:  null In Stock

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    • Ultra lightweight
    • Low friction 2-stage Orbital ball bearing system
    • Highest working load in its class
    • Easily fitted and securely retained Dyneema Link head
    • Recessed underside to suit curved or flat mounting surface


    • Safe working load: 1540 lb (700 kg)
    • Breaking load: 3080 lb (1400 kg)
    • Weight: 4.3oz (122g)
    • Sheave diameter: 2-3/4" (70 mm)
    • Maximum line size: 1/2" (12 mm)


    • Mainsheet systems and spinnaker sheets on sportsboats and small keelboats to 11m (36ft)
    • Halyard, Vang and Backstay application on boats to 9m (30ft)
    • Control line applications on larger yachts


    • High compression strength carbon black Acetal ball bearings
    • Carbon fiber reinforced, PTFE impregnated Nylon stage 2 bearing
    • Toughened glass fiber reinforced Nylon frame / cheeks
    • UV stabilized multi-strand impregnated SK75 Dyneema® rope link


    Kilogram for kilogram of working load, BB and RT Orbit Blocks are the world's lightest. To gain peak performance, we engineered out the heavy steel load straps, head post, shackle, full-length fasteners, and cleating accessories. Through extensive research and development, we replaced virtually all metal components with high-tech polymers and fiber equivalents.

    The unique orbital design allows the bearing to only be in the active areas of the floating sheave. This minimizes the mass of the inactive return race and hub.

    Weight and bulk are further reduced in the different block configurations. The ball bearing single with becket and double with becket blocks have a through-sheave becket arrangement. The result? The lowest weight possible.

    Double blocks also have only a single intermediate cheek and an ultra-light and efficient head arrangement. This gives a 30% weight saving advantage over the nearest competitor. Other brands just link together their single blocks. This results in unnecessary double cheeks between each sheave, held together by a heavy steel channel across the top of the block.

    Highest working load in its class

    The orbital ball-bearing arrangement gives the largest possible bearing race diameter. This maximizes load performance. The proven Ronstan 2-stage bearing system features high compression grade acetal ball bearings and a secondary full-contact bearing. This gives minimum friction across the full working load range.

    The floating sheave and bearing system is supported by a fiber-reinforced load frame. The design was computer modeled and optimized using stress analysis. The Dyneema® Link is produced from FSE Robline SK75 fiber, which is 10 times stronger and lighter than steel, and provides the final connection from the block to the load point.

    Simple and secure attachment

    The Dyneema® Link is easily fitted and is retained securely by a molded retainer clip. The flexible link can be left with one end attached to the block when fitting - no more lost shackle pins.

    The system is compatible with Dyneema®/Spectra® strops, webbing and carbon connection points - much more so than steel loop tops or shackles.

    Low profile and compact

    The flexible Dyneema® Link provides controlled rotation and 0° or 90° orientation. It connects directly to the head of the block rather than to an intermediate head post. This reduces weight and gives the lowest possible profile while allowing full articulation. Beckets have been carefully designed to minimize height.

    Low profile stand-up kit allows 0° or 90° alignment

    The RF2457 stand-up kit features a clatter-free rubber boot. You can attach the Dyneema® link so that the block is aligned with the stand-up base or across it. It's a neat, low-profile solution which allows full articulation.



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