Series 55 Ball Bearing

Orbit Block™


  •  Ultra Lightweight
  •  Low friction 2-stage Orbital ball bearing system
  •  Highest working load in its class
  •  Low profile and compact
  •  High performance cleating

  Product No. Desc. Sheave ØMax. Rope ØMax. Cable ØPin ØM.W.L.B. L.Weight Price RRP
 RF55101 RF55101 Single 5510--500100068 $ 54.37
 RF55110 RF55110 Single, becket, swivel head 55105500100088 $ 61.86
 RF55111 RF55111 Single, becket 5510--500100075 $ 59.03
 RF55151 RF55151 Cheek Block 5510--500100070 $ 53.42
 RF55171 RF55171 Upright lead 5510--500100091 $ 61.68
 RF55201 RF55201 Double 5510-8001600134 $ 106.85
 RF55210 RF55210 Double, becket, swivel shackle head 55105750*1500172 $ 129.43
 RF55301 RF55301 Triple 5510--10002000205 $ 169.58
 RF55310 RF55310 Triple, becket, swivel shackle head 55105750*1500 $ 185.58
 RF55410 RF55410 Quad, becket, swivel shackle head 55105750*1500316 $ 239.83
 RF55501 RF55501 Fiddle* 55 + 3510--500100095 $ 73.58
 RF55510 RF55510 Fiddle, Becket, Swivel Head 55 + 351055001000101 $ 80.85
 RF55511 RF55511 Fiddle, becket* 55 + 3510--500100097 $ 78.71
 RF55521 RF55521 Fiddle, adjustable cleat* 55 + 3510--5001000231 $ 134.52
 RF55530 RF55530 Fiddle Becket Cleat, Swivel Head* 55 + 351055001000237 $ 150.15
 RF55531 RF55531 Fiddle, becket, adjustable cleat* 55 + 35105001000223 $ 139.90

NOTE: These blocks have been specifically designed and optimised for use on racing sailboats and the conditions encountered in this unique application.  They should not be assumed suitable for other non-marine or industrial applications. For further details on associated risks see
Orbit Block Usage and Considerations


Kilogram for kilogram of working load, BB and RT Orbit Blocks™ are the world’s lightest. The unique orbital design allows the bearing to only be in the active areas of the floating sheave. This minimises the mass of the inactive return race and hub.

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

Multi-sheave blocks have only single intermediate cheeks 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 maximises 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 fibre-reinforced load frame. The design was computer modelled to be stress optimised. The Dyneema® Link is produced from FSE Robline SK75 fibre, which is 10 times stronger and lighter than steel, and provides the final connection from the block to the load point.


  • Mainsheet systems on dinghies, sportsboats and small keelboats to 9m (30ft)
  • Halyard, Vang and Backstay application on boats to 8m (26ft)
  • Control line applications on larger yachts


  • Ball bearings - High compression strength carbon black Acetal
  • Stage 2 bearing - Carbon fibre reinforced, PTFE impregnated Nylon
  • Frame/Cheeks - Toughened, glass fibre reinforced Nylon
  • Rope Link: UV stabilised, multi-strand impregmented SK75 Dyneema®


  Range Description
335 BB & RT Orbit Block™ Accessories,