Ball Bearing


Series 55 Orbit Block™, Ratchet with Becket and Cam Cleat

Single Auto Ratchet Block with Becket, Cam Cleat, Adjustable Cleat Arm, and Swivel Head


Up to 20:1 holding power.

Smooth easing of sheets.

High performance cleating.

Automatic ratchet block.


Product Specifications
B.L. (kg)750
M.W.L. (kg)250
Max. Rope diameter (mm)10
Weight (g)209
Pin Ø (mm)5
Notes:Total block load. Load on becket not to exceed block load. i.e. MWL 250kg (550lb), BL 750kg (1650lb). Suitable for 2:1 system at rated block load. Line load through cleat not to exceed 175kg (385lb).

Product Information

Automatic ratchet block

Now you can enjoy the flexibility of setting up your ratchet blocks to suit yourself. Ronstan is the only company that offers a ratchet block with both auto and manual engagement modes*. In the auto mode of the ratchet mechanism engages when load is applied, but switches off when it's released. This lets the sheet run out smoothly and freely-great for rapid easing of the sheet and for gybing asymmetric spinnakers. In manual mode, the ratchet mechanism can be switched on or off as required. This is the preferred mainsheet set-up for may top sailors. Try the block in both modes and see which you prefer - you really can't go wrong.
* Selected Series 55 models.
Awesome ratchet block holding power

Quite simply, Ronstan Ratchet Orbit Blocks™ have the highest holding power available. The sophisticated CNC-machined sheave features Generation 2 of our patented sheave cross-hole geometry. Its holding power is up to 20:1, almost double that of our nearest competitior. The unique sheave design has 12 gripping faces which directly resist loaded line movement. Traditional designes have only 8 faces with an angled resistance to line movement. Our Generation 2 design has straight resistance faces which both distribute the load and minimise rope wear. These faces are offset from the radial line, to draw the rope down into the gripping area when under load. 

Compositite C-Cleat™ and adustable cleat arm

Series 55 Ratchet Orbit Blocks™ are fitted with our carbon reinforced C-Cleat™ for secure rope holding with low entry and exit efforts, and fairlead for fast action from any angle. Cleat arms are made from the same toughened, glass fibre reinforced nylon and are adjustable for setting to your preferred cleating angle.

Technical Information


  • Dinghy mainsheet systems.
  • Spinnaker sheets on dinghies – especially modern asymmetric classes.
  • Spinnaker sheets on sportsboats and small keelboats (lateral lead blocks).
  • Control line applications on larger yachts.



  • Sheave: Anodised Aluminium.
  • Ball Bearings: High compression strength carbon black Acetal.
  • Frame / Cheeks / Cleat Arms: Toughened, glass fibre reinforced Nylon.
  • Swivel shackle head fitting: Grade 316 stainless steel.


Resource Files


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