Ball Bearing


Series 55 Orbit Block™, Single with Becket

Single, becket, swivelling shackle head


Ultra Lightweight.

Low friction 2-stage Orbital ball bearing system.

Highest working load in its class.

Low profile and compact.

High performance cleatingSwivel shackle head for unlimited block rotation.

Stainless steel shackle head and compatibility with sharp fixing points.

Ultra low profile integrated becket.


Product Specifications
B.L. (kg)1000
M.W.L. (kg)500
Max. Rope diameter (mm)10
Weight (g)88
Pin Ø (mm)5
Notes:Load on becket not to exceed 50% of block load. Suitable for 2:1 system at rated block load.

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. 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

Technical Information


Ideal use for mainsheet systems and spinnaker sheets on dinghies, sportsboats and small keel. boats to 9m (30ft). Also ideal with halyard, vang and backstay applications on boats to 8m (26ft). Spinnaker sheets on sportsboats and small keel boats (lateral lead blocks). 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®Sheave: Carbon fibre reinforced, PTFE impregnated Nylon. Head fitting: Grade 316 stainless steel. Ball Bearings: High compression strength carbon black Acetal. Stage 2 Bearing: Glass fibre reinforced, MoS2 impregnated Nylon.


Resource Files


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