Ronstan Series 20 Utility Block, Tube Rivet RF661

The Ronstan Series 20 Utility Block RF661 is a lightweight, economical, and maintenance-free single block designed for a wide range of sailing and marine applications. Featuring stainless steel cheeks, a durable Acetal sheave, and a versatile tube rivet attachment system, it provides reliable low-friction performance for control line and purchase systems.

The Ronstan Series 20 Utility Block RF661 is a simple, dependable sailing block engineered to deliver long-lasting performance with minimal maintenance. Designed for both dinghy and yacht applications, this compact single block offers an excellent balance of durability, functionality, and value.

Constructed with marine-grade 316 stainless steel cheeks and a UV-stabilised Acetal sheave, the RF661 is built to withstand harsh marine environments while maintaining smooth and reliable operation. The corrosion-resistant materials ensure a long service life, making it an ideal choice for frequently used control systems and general-purpose rigging applications.

A key feature of the RF661 is its hollow tube rivet design, which provides versatile attachment options. The rivet can accommodate fixing screws, shackles, or be used to add a becket for additional purchase configurations, allowing sailors to customise the block for various rigging requirements.

The compact 20mm sheave is designed for lines up to 5mm in diameter and provides efficient low-friction performance in lightweight purchase systems. Common applications include vang systems, Cunningham controls, trapeze retrievers, leech line tackles, bunk adjusters, and a variety of general-purpose marine rigging tasks.

Lightweight at only 10 grams, economical to purchase, and requiring virtually no maintenance, the Ronstan RF661 remains a popular choice for sailors seeking a durable and practical utility block.

Key Features

• Lightweight single utility block design
• Durable UV-stabilised Acetal sheave
• Marine-grade 316 stainless steel cheeks
• Hollow tube rivet attachment system
• Accepts screws, shackles, or optional becket configurations
• Smooth, low-friction operation
• Corrosion-resistant construction
• Virtually maintenance free
• Economical and versatile solution
• Long service life in marine environments

Ideal For

• Dinghy sailing
• Vang systems
• Cunningham controls
• Trapeze retriever systems
• Leech line tackles
• Bunk adjusters
• General marine rigging
• Small purchase systems
• Utility control lines

Technical Specifications

• Model: RF661
• Series: Ronstan Series 20 Utility Block
• Block Type: Single Tube Rivet Block
• Sheave Diameter: 20mm
• Maximum Rope Diameter: 5mm
• Maximum Working Load (MWL): 150kg
• Breaking Load (BL): 450kg
• Weight: 10g
• Sheave Material: UV-Stabilised Acetal
• Cheek Material: Grade 316 Stainless Steel