Ball Bearing


Series 55 Orbit Cheek Block

Ball bearing single sheave Orbit Block™. Requires 3 x 5mm (3/16") Fasteners.


Ultra Lightweight.

Low friction 2-stage Orbital ball bearing system.

Highest working load in its class.

Low profile and compact.

Recessed underside to suit cruved mounting surface.


Product Specifications
B.L. (kg)1000
M.W.L. (kg)500
Max. Rope diameter (mm)10
Weight (g)70
Fastener Ø (mm)5
Qty. Fasteners3

Product Information

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. 

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. 

Technical Information


  • 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.
  • Sheave: Carbon fibre reinforced, PTFE impregnated Nylon.


Resource Files


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