Ronstan RF20151A Cheek Block 20mm – Series 20 Ball Bearing Pulley

The Ronstan RF20151A Cheek Ball Bearing Pulley Block (20mm) is a compact, high-performance fixed-mount block designed for efficient control line routing on modern sailing boats.

Engineered as part of the proven Series 20 range, this block features a 20mm acetal sheave running on precision stainless steel ball bearings, delivering smooth, low-friction performance under load.

The cheek block design allows for permanent mounting directly to decks, masts, or spars, making it ideal where a fixed lead is required and space is limited.

Built with 316 stainless steel cheeks and fibre-reinforced nylon components, the RF20151A provides excellent strength, corrosion resistance, and durability in harsh marine environments.

Despite its compact size and lightweight construction (~17g), this block offers a maximum working load of 200kg and breaking load of 550kg, making it suitable for a wide range of control line applications on dinghies and small keelboats.

Designed for reliability and simplicity, the RF20151A is a go-to choice for sailors needing clean, fixed, and efficient line management.

Key Features

• 20mm ball bearing sheave – smooth, low-friction operation
• Fixed cheek block design – permanent mounting to deck or spar
• High load capacity (200kg MWL / 550kg BL)
• Compact and lightweight (~17g)
• 316 stainless steel cheeks – corrosion-resistant
• UV-stabilised acetal sheave – durable and low maintenance
• Suitable for screw or rivet mounting

Specifications

• Brand: Ronstan
• Model: RF20151A
• Series: 20 Ball Bearing
• Product Type: Cheek block (fixed pulley)
• Sheave Diameter: 20mm
• Max Rope Diameter: 6mm
• Maximum Working Load: 200kg
• Breaking Load: 550kg
• Weight: ~17g
• Materials:
  • UV-stabilised acetal sheave
  • Stainless steel ball bearings
  • 316 stainless steel cheeks
  • Fibre-reinforced nylon housing
• Mounting: Fixed (screw or rivet mount)

Ideal Applications

• Cunningham systems
• Outhaul controls
• Traveller control lines
• Deck or mast-mounted line guides
• Dinghy and skiff rigging

This block is ideal where you need a fixed, reliable, and low-friction lead for control lines.

Why Buy from Barton Marine NZ?

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

Pro Tip 

• Use cheek blocks to keep decks tidy and lines controlled
• Position carefully to ensure correct lead angle and minimal friction
• Ideal upgrade from worn plastic guides for smoother trimming performance