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Description
Ronstan 75mm Halyard Core BlockProduct Description Ronstan 75mm Halyard Core Block Features Class leading performance and sleek, contemporary styling Excellent dynamic and high static load performance Less than half the friction of the nearest competitor Durable aluminum alloy cheek plates Central hub hole can be used as a becket take off or tie up point Suits direct attachment to mainsail headboard for 2: 1 halyard Removable 8mm (5 16) threaded pin at head Acetal roller on head
Product Description
Ronstan 75mm Halyard Core Block
Features
Class leading performance and sleek, contemporary styling
Excellent dynamic and high static load performance
Less than half the friction of the nearest competitor
Durable aluminum alloy cheek plates
Central hub hole can be used as a becket take-off or tie-up point
Suits direct attachment to mainsail headboard for 2:1 halyard
Removable 8mm (5/16”) threaded pin at head
Acetal roller on head pin to suit spliced line attachment
Alloy Rope/Wire sheave version also available
Measurements
Sheave Ø - 3 in. (78 mm)
Max. Rope Ø - 9/16 in. (14 mm)
Max. Cable Ø - in (mm)
Pin Ø - 5/16 in. (8 mm)
M.W.L. - 330 lb. (1500 kg)
B. L. - 6600 lb. (3000 kg)
Weight - 8.6 oz. (234 g)
Product Information
Core Blocks™ are a true all round solution. A tuned 2-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. Acetal sheave, alloy cheeks and stainless fixings complete the durable package. For reliability and a long service life, these blocks are the right choice for sheets, halyards and control line applications for cruising and racing.
Universal Bearing
Dynamic and high static load performance
The Ronstan Universal Bearing incorporates our proven 2-stage bearing system
Stage 1 - Under moderate loads, Acetal ball bearings ensure minimum friction.
Stage 2 - Under heavy loads, where deformation of ball bearings alone would result in increased friction, a sliding Acetal bearing on a polished stainless steel race takes over, maintaining low friction performance.
Additionally the ball bearings are configured to act as a thrust bearing between the sheave and cheeks, preventing the sheave from rubbing on the cheeks and causing friction when the line lead in and out of the block isn’t perfect. Particularly important for cheek blocks.
Alloy cheek plates
Block cheeks are manufactured from the highest quality alloy for maximum strength. Material optimization and the cut-away design minimizes weight and allows easy fresh water rinsing of salt and debris from the bearings. Cheek design has been further styled with flaring at the block throat and reduced gap between the cheek and sheave, minimizing rope wear.
Applications
Ideal for use on mainsheet, spinnaker sheet, vang, halyard and backstay applications on boats up to 14m (46ft).
General applications on larger yachts.
Alloy sheave models are available for use with wire.
Materials
Sheave: U.V. stabilized acetal or anodized aluminum (AW models).
Cheek plates: Aluminum alloy
Ball Bearings: High compression strength carbon black acetal.
Pin: 2205 stainless steel
Features
Measurements
Sheave Ø - 3 in. (78 mm)
Max. Rope Ø - 9/16 in. (14 mm)
Max. Cable Ø - in (mm)
Pin Ø - 5/16 in. (8 mm)
M.W.L. - 330 lb. (1500 kg)
B. L. - 6600 lb. (3000 kg)
Weight - 8.6 oz. (234 g)
Product Information
Core Blocks™ are a true all round solution. A tuned 2-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. Acetal sheave, alloy cheeks and stainless fixings complete the durable package. For reliability and a long service life, these blocks are the right choice for sheets, halyards and control line applications for cruising and racing.
Universal Bearing
Dynamic and high static load performance
The Ronstan Universal Bearing incorporates our proven 2-stage bearing system
Stage 1 - Under moderate loads, Acetal ball bearings ensure minimum friction.
Stage 2 - Under heavy loads, where deformation of ball bearings alone would result in increased friction, a sliding Acetal bearing on a polished stainless steel race takes over, maintaining low friction performance.
Additionally the ball bearings are configured to act as a thrust bearing between the sheave and cheeks, preventing the sheave from rubbing on the cheeks and causing friction when the line lead in and out of the block isn’t perfect. Particularly important for cheek blocks.
Alloy cheek plates
Block cheeks are manufactured from the highest quality alloy for maximum strength. Material optimization and the cut-away design minimizes weight and allows easy fresh water rinsing of salt and debris from the bearings. Cheek design has been further styled with flaring at the block throat and reduced gap between the cheek and sheave, minimizing rope wear.
Applications
Materials
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.4 ★★★★★
Based on 14 reviews
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Product Reviews
★★★★★ 4
Great for indoor use.
Size: 10-11, Color: Cable Knit Navy
I bought a pair of these for myself about a year ago and there are plusses and minuses to them. They are comfortable and warm, without getting my feet sweaty or whatever. That's exactly what I wanted. On the minus side, mine ran far too small. I am a 10.5-11 shoe size and the 10-11 is about a half inch too short... my heels are sliding off the back. I am reordering a size 12-13 to try that one. In the take note column, the soles are NOT rubberized in any way. In fact they are like foam, and will absorb water! Also they do not provide cushioning against any kind of rough surface. I think they are perfect for strictly inside the apartment use, but they are not like moccasins or something that allow outdoor use. And I am ordering a 2nd pair after a year so I do like them.
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Reviewed in the United States on November 24, 2025
★★★★★ 5
They are of great quality!
Size: 12-13, Color: Cable Knit Coffee
Love em! After a year and there still Great and warm and Cozy too!
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Reviewed in the United States on May 26, 2026
★★★★★ 5
Wonderful sock slippers
Size: 12-13, Color: Cable Knit Navy
These are wonderful sock slippers, They are very warm and well made. After reading reviews, I decided to order one size larger (10 to 11) and they are really comfortable big. However, I'm glad I did because they a lot easier to put on and take off. Highly recommended.
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Reviewed in the United States on April 20, 2026
★★★★★ 3
You get what you pay for
Size: 10-11, Color: Cable Knit Black
Comfy but cheaply made. I bought these for the price and expected them to be not the best quality but they are even less than I expected. Please also note that they run small. I got a 10-11 since I wear 11 shoe and Amazon recommended this size. I think a size larger would have been better. Not worth returning though. I’ll just wear them this winter if they last that long and get a better brand next time.
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Reviewed in the United States on December 25, 2025
★★★★★ 5
I will buy these again.
Size: 12-13, Color: Cable Knit Brown
These are great. They’re warm and comfortable.
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Reviewed in the United States on May 5, 2026