Ronstan RF20100 Single Swivel Pulley 20mm – Series 20 Ball Bearing Block

The Ronstan RF20100 Single Swivel Ball Bearing Pulley (20mm) is a compact, high-performance Series 20 block designed for dynamic sailing applications where free movement and alignment are essential.

Built with a 20mm acetal sheave running on precision stainless steel ball bearings, this block delivers exceptionally low friction and smooth operation, ensuring efficient load handling even under demanding conditions.

The key feature of the RF20100 is its swivel shackle head, which allows the block to rotate freely under load. This ensures optimal line alignment, reduced twisting, and improved efficiency, especially in constantly changing load directions.

Constructed using UV-stabilised acetal, fibre-reinforced nylon cheeks, and 316 stainless steel load components, the RF20100 is engineered for durability, corrosion resistance, and long service life in harsh marine environments.

With a maximum working load of 250kg and breaking load of 550kg, this lightweight (~20g) block offers an excellent balance of strength, performance, and weight, making it a go-to choice for dinghies, skiffs, and small keelboats.

Key Features

• 20mm ball bearing sheave – smooth, low-friction operation
• Swivel shackle head – self-aligns under load for efficiency
• High load capacity (250kg MWL / 550kg BL)
• Lightweight (~20g) – ideal for performance sailing
• UV-stabilised acetal sheave – durable and low maintenance
• 316 stainless steel components – corrosion-resistant
• Compact design – perfect for tight rigging setups

Specifications

• Brand: Ronstan
• Model: RF20100
• Series: 20 Ball Bearing
• Product Type: Single pulley block with swivel head
• Sheave Diameter: 20mm
• Max Rope Diameter: 6mm
• Pin Diameter: 3.0mm
• Maximum Working Load: 250kg
• Breaking Load: 550kg
• Weight: ~20g
• Materials:
  • UV-stabilised acetal sheave
  • Stainless steel ball bearings
  • 316 stainless steel load strap
  • Fibre-reinforced nylon cheeks

Ideal Applications

• Vang systems
• Cunningham and outhaul controls
• Traveller systems
• Sheet leads and control lines
• Dinghy and skiff rigging

This block is ideal where you need maximum flexibility and automatic alignment in dynamic control systems.

Why Buy from Barton Marine NZ?

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

Pro Tip 

• Use swivel blocks where line angles change frequently
• Ideal upgrade from fixed blocks to reduce friction and wear
• Pair with low-stretch Dyneema rope for best performance