The Ronstan RF104110 Series 100 Core Block with Becket (100mm) is a heavy-duty, high-load sailing pulley engineered for demanding offshore, cruising, and racing applications. Designed as part of Ronstan’s premium Core Block™ range, it delivers exceptional strength, ultra-smooth operation, and long-term durability under extreme loads.

Featuring a 100mm glass fibre reinforced acetal sheave with a two-stage bearing system, this block provides low friction performance across both light and heavy loads. The integrated ball bearing and sliding bearing system ensures efficiency even under high load conditions, maintaining smooth line handling in critical sailing systems.

Constructed with hard-anodised aluminium alloy cheeks and stainless steel components, the RF104110 is built to withstand harsh New Zealand marine environments. The integrated becket allows easy tie-off or multi-part purchase systems, making it ideal for complex rigging setups.

Perfect for mainsheets, halyards, vangs, and runner systems, this block is commonly used on keelboats, offshore yachts, and performance cruisers up to ~16m.

Key Features

• 100mm sheave for high-load applications
• Two-stage bearing system for low friction across load ranges
• Integrated becket for tie-off and purchase systems
• Aluminium alloy cheeks for maximum strength and reduced weight
• Ball bearings act as thrust bearings to reduce side-load friction
• Universal head with 360° rotation and locking positions
• Suitable for pre-spliced lines with removable becket pin
• Designed for offshore, racing, and high-performance sailing

Specifications

• Sheave Diameter: 100mm
• Max Rope Diameter: 18mm
• Maximum Working Load: 3250kg
• Breaking Load: 7500kg
• Weight: approx. 1098g
• Pin Diameter: 10mm
• Construction: Acetal sheave, alloy cheeks, stainless fittings
• Type: Single block with becket and universal head

Why Choose the Ronstan RF104110? 

For New Zealand sailors operating in coastal and offshore conditions, the RF104110 delivers maximum reliability under extreme loads. Its advanced bearing system ensures smooth performance even when heavily loaded, making it ideal for critical sail handling systems.

This block is a premium choice for sailors who demand strength, efficiency, and long-term durability, whether cruising offshore or racing competitively.