Ronstan Series 55 Orbit Single Swivel Head Block
- Ultra Lightweight
- Low friction 2-stage Orbital ball bearing system
- Highest working load in its class
- Easily fitted and securely retained Dyneema Link head
- Low profile and compact
- 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 becket.
- Sheave Diam: 55 mm
- Max. Rope Diam: 10mm
- Max. Wire Diam: - mm
- Pin Diam: - mm
- Max. Working Load: 500 kg
- Breaking Load: 1000 kg
- Weight: 88 g
Kilogram for kilogram of working load, BB and RT Orbit Blocks™ are the world’s lightest. To gain peak performance, we engineered out the heavy steel load straps, head post, shackle, full-length fasteners, and cleating accessories.
Through extensive research and development, we replaced virtually all metal components with high-tech polymers and fibre equivalents.
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.
Simple and secure attachment
The Dyneema® Link is easily fitted and is retained securely by a moulded retainer clip. The flexible link can be left with one end attached to the block when fitting - no more lost shackle pins.
The system is compatible with Dyneema®/Spectra® strops, webbing and carbon connection points - much more so than steel loop tops or shackles.
Low profile and compact
The flexible Dyneema® Link provides controlled rotation and 0° or 90° orientation. It connects directly to the head of the block rather than to an intermediate head post. This reduces weight and gives the lowest possible profile while allowing full articulation. Beckets have been carefully designed to minimise height.
- Mainsheet systems on dinghies, sportsboats and small keelboats to 9m (30ft)
- Spinnaker sheets on dinghies, sportsboats and small keel boats to 9m (30ft)
- Halyard, Vang and Backstay application on boats to 8m (26ft)
- Ideal use for mainsheet systems and spinnaker sheets on dinghies, sportsboats and small keel
- Control line applications on larger yachts
- Also ideal with halyard, vang and backstay applications on boats to 8m (26ft).
- Spinnaker sheets on sportsboats and small keel boats (lateral lead blocks)
- 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.
Australia Post and our Commercial Couriers are expecting the festive season to be extra busy this year. Based on their advice, we cannot guarantee orders placed after the cut-off dates listed below will be delivered by Christmas.
To avoid disappointment place your Christmas orders as early as possible.
Overseas, offshore islands and distant mainland locations may take up to 3 or 4 weeks to deliver. Please contact your local Mail Order Department to discuss specific details relating to your situation.
All orders are shipped from our Brookvale, Sydney order fulfilment centre. Orders are normally shipped within 5 business days - most quicker!
Shipping day estimates after your order leaves our fulfilment centre in Sydney are based on Australia Post domestic delivery times:
|ACT||2 - 3 business days||1 - 2 business days|
|NSW||2 - 4 business days||1 - 3 business days|
|NT||4 - 13 business days||3 - 5 business days|
|QLD||3 -12 business days||2 - 4 business days|
|SA||3 - 5 business days||2 - 4 business days|
|TAS||4 - 8 business days||2 - 4 business days|
|VIC||3 - 5 business days||2 - 3 business days|
|WA||5 - 10 business days||2 - 6 business days|
Last updated 12/09/2023
* These delivery times are an estimate and actual delivery times may vary based on peak periods and other external factors. Bulky orders may take longer.
Shipping rates are automatically calculated based on live quotes supplied by our shipping partners. The quote takes into consideration, the bulk of your cart, where you want it delivered and if you want express or standard shipping.
Get a shipping rate estimate by adding items to your online cart. Go to the cart by clicking on the shopping cart icon located at the top right of the page. Then enter your shipping destination information into the "Estimate Shipping and Tax" section of the shopping cart summary.
We are currently unable to deliver online orders outside of Australia.
If you are located outside of Australia and wish to place an order offline. Please contact our Mail Order department or send us an enquiry via the orange help bubble located at the bottom right of this page.
Online purchases can be returned/exchanged within 30 days. Some exclusions do apply.
Visit our Returns Policy page for details on how you can return an item.