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Ships within 48 hours · Estimated delivery Aug 18 - Aug 23
For Your Every Summer RSVP, with Code: SUMMER15
Description
Ronstan Series 45 Core Block - Single - Swivel Shackle HeadSeries 45 Core Block Single Swivel Shackle Head 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,
Series 45 Core Block - Single - Swivel Shackle HeadCore 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.
Features:
- High dynamic and static load capacity
- Efficient 2-stage bearing system
- Ball bearings to counteract side thrust loads
- Class leading performance and sleek, contemporary styling
- Durable aluminium alloy cheek plates
- 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 10M (33')
- Various control line applications on larger yachts
- Alloy sheave models are available for use with wire
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: 45mm(1-3/4")
Max. Rope Ø: 12mm(1/2")
Pin Ø: 5mm(3/16")
M.W.L.: 700kg(1,540lbs)
B. L.: 1,400kg(3,090lbs)
Weight: 104g(3.6oz)
Manufacturer : Ronstan
Manufacturer Part No : RF44100
UPC : 9316800466153
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
4.2 ★★★★★
Based on 19 reviews
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Product Reviews
★★★★★ 5
Soft and cool. Very cool. 🧊
Size: Queen, Color: White
I bought these for my memory foam pillow and they’re excellent for cooling it. I use 2 of these on the pillow for maximum chill factor and it works.
They’re very soft, the zippers are high quality. Easy to put on with a bit of stretch- generously sized. They’re stain resistant. I’m glad they’re NOT waterproof because they’d be too hot then. They’re very durable. Wash on delicate setting in a mesh bag and air dry and they last long. They’re very quiet- smooth and silky. Definitely recommend!
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Reviewed in the United States on January 15, 2026
★★★★★ 3
Cool enough
Size: Queen, Color: White, Size: Queen, Color: White
I thought I had purchased pillows so when I received these I was a little disappointed. However that was 100% on me for not reading the listing and just trusting my search. I decided to give them a try and so far they seem ok. They don’t stay cool even though I have them on cooling pillows. They are super thin but very soft. They fit on my pillows perfectly. I don’t think it has improved my sleep quality but it hasn’t made it any worse either. I don’t think they are waterproof but I don’t really want to test that. I like that the zipper is small and seems to be decent quality. Smelled heavily of chemicals when I first took it out of the package but that disappeared after a few minutes.
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Reviewed in the United States on March 21, 2026
★★★★★ 5
Sleep like a baby
Size: Queen, Color: White
These pillow covers are cool. They keep you cool at night. very, very comfortable.
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Reviewed in the United States on May 13, 2026
★★★★★ 5
Very well made.
Size: King, Color: White
These work great and look good.
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Reviewed in the United States on April 27, 2026
★★★★★ 5
Great pillow!
Size: Queen (Pack of 2)
They were a gift for my daughter and she loves them! She says they are comfortable and "squishy" and she sleeps better on them.
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Reviewed in the United States on May 5, 2026