SKU: 36179294442

Ronstan Series 75 Core Block - Single

Sale price$138.47 Regular price$153.85
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Ships within 48 hours · Estimated delivery Aug 16 - Aug 21

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Description

Ronstan Series 75 Core Block - SingleSeries 75 Core Block Single 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

Series 75 Core Block™ - Single

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 optimisation and the cut-away design minimises 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, minimising rope wear.

Universal head
The head assembly incorporates a brass bearing washer to provide smooth 360™ rotation of the post and shackle. A set screw arrangement allows the head to be locked at 0™ or 90™.

Shackles are high quality forged grade 316 stainless steel.

Features:

  • Class leading performance and sleek, contemporary styling
  • Excellent dynamic and high static load performance
  • Less than half the friction of the nearest competitor
  • Universal head with full 3-axis articulation
  • Head posts can be locked at 0 or 90 degrees, by using a 2.5mm Hex/Allen Key
  • Central hub hole can be used as a becket take-off or tie-up point


Applications:
  • Ideal for mainsheet, halyard and spinnaker sheet applications on boats to 14M (46')
  • Various control line applications on larger yachts


Materials:
  • Sheave: U.V. stabilized Acetal
  • Cheek body: Aluminium Alloy
  • Ball Bearings: High compression strength carbon black Acetal
  • Shackle, head post & hub: Grade 316 stainless steel


Specifications:
Sheave Ø: 75mm(3")
Max. Rope Ø: 14mm(9/16")
Pin Ø: 8mm(5/16")
M.W.L.: 1,500kg(3,300lbs)
B. L.: 3,000kg(6,600lbs)
Weight: 354g(12.5oz)

Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. 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
SKU: 36179294442

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Heather260
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★★★★★ 5
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The only no show socks I have ever found that do not slide down. These are very comfortable and the extra tab on the back provides comfort by keeping shoes from rubbing the back of your foot. The top of the sock also comes up high enough to cushion the top of your foot all while still remaining hidden while wearing tennis shoes or even with my hey dudes.
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Reviewed in the United States on November 30, 2025
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Nick
Bozeman, US
★★★★★ 5
Great quality and fast shipping
Size: Medium, Color: (001) Black / Black / Castlerock
These socks are tight but after the first wash and dry , they fit perfect and NEVER slide off , ordered a second pack
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Reviewed in the United States on March 24, 2026
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Bargain Rig
Los Angeles, US
★★★★★ 5
Comfortable, Durable, and Stylish
Perfect gift choice! Excellent quality socks with a variety of colors to match any wardrobe.
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Reviewed in the United States on November 30, 2025
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Maranda
Birmingham, US
★★★★★ 5
Great fit
Size: Medium, Color: White
Perfect fit and they don't slide off the back of your ankle.
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Reviewed in the United States on March 16, 2026
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Jessica Burdett
Lake Worth, US
★★★★★ 5
Best socks!
Size: Medium, Color: Blue
I love these socks! They last for years and they fit so nicely on my feet. I love that I can wear the in tennis shoes or wool boots and they never move!
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Reviewed in the United States on October 21, 2025

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