Ronstan Series 40 Ball Bearing Block - Triple - Swivel Head

The Ronstan Series 40 Ball Bearing Block – Triple – Swivel Head is a precision marine pulley system engineered for sailors and boaters who demand reliability under load. Whether you're managing halyards, sheets, or control lines on cruising yachts, racing dinghies, or commercial fishing vessels, this triple block delivers the mechanical advantage and smooth operation that separates confident seamanship from struggle. The swivel head design eliminates twist and torque in your rigging, reducing wear on hardware and line alike—a critical feature when you're far from port.

At its core, the Series 40 features low-friction Acetal or Torlon® ball bearing sheaves that dramatically reduce friction compared to standard bushed blocks. The three-sheave configuration provides a 6:1 purchase ratio, allowing you to hoist sails, anchor loads, or tender hoists with significantly less physical effort. Cheek cut-outs provide simple access to bearings for periodic maintenance—no need to haul the block off the boat for routine inspection. The rigid yet lightweight construction (just 0.4 lbs) minimizes weight aloft, a crucial consideration for performance and safety in any vessel's rigging plan.

Cruising sailors, racing crews, and commercial operators benefit most from this block's durability and ease of maintenance. The swivel shackle head rotates a full 360 degrees, accommodating dynamic line angles without binding or creating stress concentrations that accelerate hardware failure. At 3 x 2 x 5 inches, it integrates cleanly into cabin sole systems, boom gallows rigging, and davit arrangements. This block is a proven choice for deck hardware that performs reliably across seasons and miles of hard sailing.