Lewmar 29925004BK 50mm Synchro Single Block with Becket

The Lewmar 29925004BK is a 50mm Synchro Single Block with Becket, engineered for sailors who demand racing-level performance at a cruising-friendly price point. Part of Lewmar's acclaimed Synchro Block series, this block represents a ground-up rethink of traditional block design to maximize speed, efficiency, and ease of handling in running rigging applications.

At the heart of the Synchro design is a combination of scientifically optimized block geometry, a Free-Spin high-density bearing, and a self-aligning swivel head that work together to reduce friction and improve system efficiency by up to 40% compared to conventional mainsheet blocks. Every component is synchronized with the movement of the rope, delivering a smoother transfer of power from deck to sail while minimizing wear on both the line and the block itself.

Key Features:

• Free-Spin bearing: High-density, self-lubricating bearing reduces axle diameter for superior mechanical efficiency
• Self-aligning swivel head: Innovative sliding lock mechanism allows selection between full 360° free rotation or fixed positions at 0° or 90° to the sheave axle
• 30° rotational float: Both fixed positions provide 30° of float so the block can self-align within the system
• Larger sheave diameter (50mm): Minimizes rope friction and works well with lines up to 3/8" (10mm)
• Stainless steel straps: Improved strength and extended service life
• Glass fiber reinforced cheeks: Stiff construction prevents lines from wedging
• Becket included: Provides an anchor point for the standing end of a purchase system
• Black finish (BK): Clean, low-profile appearance suited to modern sailboat hardware

The Lewmar 29925004BK is well-suited for mainsheet systems, boom vangs, halyard tuning, and other purchase systems where friction reduction and smooth rope travel are critical. The addition of the becket makes this block ideal as the lower block in a multi-part tackle arrangement. A tool-free sliding swivel locking mechanism makes adjustments quick and easy on the water.