Ronstan RF20312 Triple Block with Becket 20mm – Series 20 Ball Bearing Pulley

The Ronstan RF20312 Triple Ball Bearing Block with Becket (20mm) is a compact, high-performance pulley designed for powerful purchase systems on modern sailing boats.

Part of the trusted Series 20 range, this block features three 20mm acetal sheaves running on precision ball bearings, delivering exceptionally low friction and smooth operation—ideal for high-load, fast-adjusting control lines.

The integrated becket provides a fixed tie-off point, enabling efficient cascading systems and increased mechanical advantage without adding extra hardware.

Designed for versatility, the RF20312 includes a 2-axis shackle head that can be fixed at 0° or 90°, allowing optimal alignment with the load direction for improved performance and reduced wear.

Built with UV-stabilised acetal sheaves, fibre-reinforced nylon cheeks, and 316 stainless steel load components, this block is engineered to handle high static and dynamic loads while remaining lightweight and corrosion-resistant.

With a maximum working load of 400kg and breaking load of 850kg, the RF20312 offers exceptional strength in a compact form—perfect for demanding sailing applications.

Key Features

• Triple 20mm sheaves – high mechanical advantage for control systems
• Ball bearing system – ultra-low friction and smooth operation
• Integrated becket – efficient line termination and purchase setup
• 2-axis shackle head – adjustable alignment (0° or 90°)
• High load capacity (400kg MWL / 850kg BL)
• Lightweight design (~64g)
• Durable composite construction – corrosion-resistant and UV-stable

Specifications

• Brand: Ronstan
• Model: RF20312
• Series: 20 Ball Bearing
• Product Type: Triple block with becket
• Sheave Diameter: 20mm
• Max Rope Diameter: 6mm
• Pin Diameter: 4.0mm
• Maximum Working Load: 400kg
• Breaking Load: 850kg
• Weight: ~64g
• Materials:
  • UV-stabilised acetal sheaves
  • Stainless steel ball bearings
  • 316 stainless steel load strap
  • Fibre-reinforced nylon cheeks

Ideal Applications

• Vang systems
• Cunningham and outhaul controls
• Mainsheet purchase systems
• Traveller systems
• High-performance dinghy and skiff rigging

This block is ideal where you need maximum mechanical advantage without the added bulk of larger hardware.

Why Buy from Barton Marine NZ?

• Trusted NZ Ronstan supplier
• Fast nationwide delivery
• Genuine high-performance sailing hardware
• Ideal for NZ racing and cruising conditions

Pro Tip 

• Use in cascading systems to maximise purchase efficiency
• Align the block using the 2-axis head to reduce friction and wear
• Pair with low-stretch Dyneema lines for optimal performance