Ball Bearing


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

Triple Ratchet Block with underhung becket, adjustable cleat, auto ratchet, swivel


Up to 20:1 holding power.

Smooth easing of sheets.

High performance cleating.

Swivel shackle head for unlimited block rotation.

Stainless steel shackle head for ultimate durability and compatibility with harsh fixing points.

Ultra low profile integrated beckets.


Product Specifications
B.L. (kg)1500
M.W.L. (kg)750*
Max. Rope diameter (mm)10
Weight (g)392
Pin Ø (mm)5
Notes:Load on underhung becket not to exceed 33% of block load. i.e. MWL 250kg (700lb), BL 500kg (1100lb). Underhung becket suits attachment of ‘piggyback’ block for creation of 7:1 or greater purchase. 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


  • Mainsheet systems and spinnaker sheets on dinghies, catamarans, sportsboats and small keel boats to 9m (30ft).
  • RF55410, when paired with a RF56330B and a RF35101 lashed to the becket, produces a powerful 8:1 mainsheet system for use on catamarans to 5.5m (18ft). This can be increased to 9:1 by replacing the RF35101 with a RF45201.
  • Halyard, vang and backstay applications on boats to 8m (26ft).
  • Control line applications on larger yachts.



  • Ratchet 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


Need some advice?

Send us a

Find a