Series 40 All-Purpose Single Block


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Model # 271754 | Mfg # RF41100 | UPC # 9316800242870

General application plain-bearing blocks provide performance and value.

A smooth and efficient block is critical to the conversation between sailor and boat—especially for handheld control lines. Ronstan designed the Series 40 All-Purpose blocks to give dinghy and small keelboat sailors the feedback to detect subtle wind changes and sail as efficiently as possible.

These lightweight blocks feature a durable, self-lubricating, UV stable acetal sheave that runs smoothly on a Grade 316 stainless steel shaft. Fiber reinforced nylon cheeks provide rigidity and strength and are beefed up with 316 stainless steel load straps. The included shackle features a screw pin with a low-profile head to prevent snagging on smaller lines. Get the messages your boat sends you though the lines by using efficient and smooth Ronstan Series 40 All-Purpose blocks.

This 40mm single with shackle head is versatile and can be used for a wide range of applications. Great for halyard tuners, Cunninghams, dinghy sheets and more. 

Key Features

  • Lightweight blocks designed for moderate to high static and dynamic loads
  • Ideal for handheld control lines
  • Captive lock secures swivel at  0° or 90° or left to swivel freely
  • Sliding acetal plain bearing on 316 stainless steel shaft handles high loads and maintains low friction
  • Fiber reinforced nylon cheeks to add strength while reducing weight
  • Self-lubricating, UV stable acetal sheave is strong and lightweight
  • Grade 316 stainless steel load straps add strength
  • Ideal for: Dinghy and small keelboat sheets, halyard tuning systems, backstay systems on dinghies and smaller keelboats, boom vangs (cascade systems)


Series 40 All-Purpose Single Block

Name Value
Ball Bearings Plain Bearings
Becket No Becket
Diameter 7/16 Inch or 11 mm
Direction Any
Integral Cleat No Integral Cleat
Mount Type Swivel Shackle
Ratchet Non Ratcheting
Safe Working Load 882 Pounds
Sheave Diameter 40 mm
Type Single
Weight 2.5 Ounces


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