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Ronstan "Orbit" Ratchet Blocks - Auto & Manual - 55mm

Ronstan "Orbit" Ratchet Blocks - Auto & Manual - 55mm

SKU: 504703

$85.16 / EA

Ratchet Orbit Block™ - Series 55 RT

Automatic & Manual Ratchet in One Block

Automatic and manual ratchet options Ronstan offers a ratchet block with both auto and manual engagement modes. In automatic mode, the ratchet mechanism engages when load is applied but switches off when it's released. This lets the sheet run out smoothly and freely, which is 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 many top sailors.

Awesome ratchet block holding power
Ronstan Ratchet Orbit Blocks® have the highest holding power available. The sophisticated NC-machined sheave features Generation 2 of their patented sheave cross-hole geometry. The Series 55 delivers up to 20:1 holding power, almost double that of Ronstan's nearest competitior.

The unique sheave design has 12 gripping faces, which directly resist loaded line movement. Traditional designs have only 8 faces with an angled resistance to line movement. Ronstan's Generation 2 design has straight resistance faces, which both distribute the load and minimize rope wear. These faces are offset from the radial line in order to draw the rope down into the gripping area when under load.

Smooth easing of sheets
With auto models, the sheet runs out smoothly and freely as soon as the ratchet mechanism disengages. When engaged, and with manual models, the sheave cross-hole geometry eliminates the "shuddering" ease-out that you can expect from traditional v-groove ratchet blocks.

RF56100 - Swivel shackle head for unlimited block rotation
Grade 316 stainless steel shackle head for ultimate durability and compatibility with harsh fixing points.


  • Automatic & Manual Ratchet in one block
  • Swivel shackle head for unlimited block rotation - RF56100
  • Up to 20:1 holding power


  • Sheave - Hard-anodized aluminum
  • Ball Bearings - High-compression-strength carbon black Acetal
  • Frame/Cheeks - Toughened, glass-fibre-reinforced Nylon
  • Rope/Link - UV-stablized, multi-strand impregnated SK75 Dyneema®


  • Mainsheet systems & spinnaker sheets on dinghies, sport boats & small keelboats to 26 feet (8m)
  • Halyard, vang & backstay applications on boats to 26 feet (8m)
  • Spinnaker sheets on sportsboats & small keel boats (lateral lead

Mfg No. RF56100

Description Single / swivel head

Sheave Diameter 2-5/32" (55mm)

Max Rope Diameter 3/8" (10mm)

Max Working Load 550 Lbs (250kg)

Breaking Load 1,430 Lbs (650kg)

Weight 2.9 oz. (82g)

* Total block load. Load on becket not to exceed block load, i.e., MWL 550 Lbs (250kg), BL 1,650 Lbs (750kg). Suitable for 2:1 system at rated block load.

/ EA
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