Ronstan Series 75 Core Block - Single

The Series 75 Core Block™ – Single is the ultimate solution for marine and boating applications, offering unparalleled performance and durability. Designed with a precision-tuned 2-stage bearing system, this block ensures smooth operation across a wide range of loads. Whether you're cruising or racing, the Core Block™ provides reliable handling for sheets, halyards, and control lines, making it an essential addition to any vessel.

Exceptional Bearing Performance

The Ronstan Universal Bearing within the Series 75 Core Block™ features a proven 2-stage system that delivers both dynamic and high static load performance:

Stage 1

Under moderate loads, acetal ball bearings minimize friction, ensuring smooth maneuvering of lines.

Stage 2

When subjected to heavy loads, a sliding acetal bearing on a polished stainless steel race takes over, maintaining low friction and preventing deformation of the ball bearings. This dual-stage approach ensures consistent performance even under the most demanding conditions.

Additionally, the ball bearings function as a thrust bearing between the sheave and cheeks, eliminating friction caused by imperfect line lead-ins and lead-outs. This feature is particularly beneficial for cheek blocks, enhancing overall reliability.

Durable Alloy Cheek Plates

Constructed from high-quality aluminum alloy, the cheek plates offer maximum strength while maintaining a lightweight design. The optimized material and cut-away design facilitate easy rinsing with fresh water, effectively removing salt and debris from the bearings. The flared block throat and reduced gap between the cheek and sheave minimize rope wear, prolonging the lifespan of both the block and your lines.

Universal Head Assembly

The universal head of the Series 75 Core Block™ incorporates a brass bearing washer, allowing for smooth 360° rotation of the post and shackle. A set screw mechanism enables the head to be securely locked at 0° or 90°, providing versatile positioning options. High-quality forged grade 316 stainless steel shackles ensure durability and resistance to marine environments.

Key Features

• Class-leading performance with 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° using a 2.5mm Hex/Allen Key
• Central hub hole serves as a becket take-off or tie-up point

Ideal Applications

• Perfect for mainsheet, halyard, and spinnaker sheet applications on boats up to 14 meters (46 feet)
• Suitable for various control line applications on larger yachts

Premium Materials

• Sheave: U.V. stabilized Acetal
• Cheek Body: Aluminum Alloy
• Ball Bearings: High compression strength carbon black Acetal
• Shackle, Head Post & Hub: Grade 316 stainless steel

Technical Specifications

Specification	Details
Sheave Ø	75mm (3")
Max. Rope Ø	14mm (9/16")
Pin Ø	8mm (5/16")
Maximum Working Load (MWL)	1,500kg (3,300lbs)
Breaking Load (B.L.)	3,000kg (6,600lbs)
Weight	354g (12.5oz)

Orders of physical products placed by 3 PM EST M-F typically ships the same day, if all requested items are in stock. Weekend orders will typically ship on Monday.

Shipping takes 2-7 days.

We currently ship to the Contiguous 48 States.

Life of Sailing merch is custom made for the customer after an order is placed. Total turnaround is typically 7-14 days from order to doorstep.