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Description
Ronstan 75mm Double, Non-Swivel Head Core BlockProduct Description Ronstan 75mm Double, Non Swivel Head 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 Removable threaded pin at shackle head Central hub hole can be used as a becket take off point. Measurements
Product Description
Ronstan 75mm Double, Non-Swivel Head 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
Removable threaded pin at shackle head
Central hub hole can be used as a becket take-off point.
Measurements
Sheave Ø - 3 in. (75 mm)
Max. Rope Ø - 9/16 in. (14 mm)
Max. Cable Ø - in (mm)
Pin Ø - in. (mm)
M.W.L. - 330 lb. (1500 kg)
B. L. - 6600 lb. (3000 kg)
Weight - 17.9 oz. (506 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. (75 mm)
Max. Rope Ø - 9/16 in. (14 mm)
Max. Cable Ø - in (mm)
Pin Ø - in. (mm)
M.W.L. - 330 lb. (1500 kg)
B. L. - 6600 lb. (3000 kg)
Weight - 17.9 oz. (506 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 23 reviews
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Product Reviews
★★★★★ 5
LOVE THEM!!
Size: Small, Color: (001) Black / Black / Castlerock
LOVE! These socks are so comfortable! I wear a 5 in women's and a 3 in big kid shoes. The small fit me perfectly. I see where some say they run small but I can't say that was an issue for me. They are "snug" but thats what you want with a no show sock. I feel they have support vs the ones i used to buy at Walmart. They are very soft! I am actually buying more today and throwing my other ones in the trash!
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Reviewed in the United States on February 18, 2026
★★★★★ 5
So will not write down your foot
Size: Medium, Color: (001) Black / Black / Castlerock
I love these socks. They have a little bit of gel on the top of the heel for support in your tennis shoes and so your socks don’t write down. Very good quality.
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Reviewed in the United States on May 6, 2026
★★★★★ 5
Comfy and Stay Put
Size: Medium, Color: (002) Black / Black / Halo Gray
These socks are honestly great. They’re super thin and light, so once you have them on, you kind of forget they’re even there. No bulky feeling in your shoes at all.
The best part is they actually stay on. I hate no-show socks that slide down after five minutes, and these don’t do that. The little grip on the heel really works, so you’re not constantly adjusting them all day.
They’re breathable too, which is nice if your feet run warm. They dry fast and don’t get that gross sweaty feeling. And there’s no annoying seam on the toe, so nothing rubs or feels uncomfortable.
Basically, they’re just comfy, stay put, and don’t cause problems — which is all I want from socks.
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Reviewed in the United States on January 16, 2026
★★★★★ 5
Perfect sucks
Size: Medium, Color: (001) Black / Black / Castlerock
Wonderful socks . The weight is perfect !! These do not slip when in a shoe they stay out !!
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Reviewed in the United States on April 14, 2026
★★★★★ 4
Amazing but quality changed
Size: Large, Color: (002) Black / Black / Halo Gray
Love these socks so much, been buying them for about 4 years now!! Not giving them 5 stars anymore because the quality is different and not as good, durable and thick as before.
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Reviewed in the United States on July 10, 2025