Lewmar 50mm Synchro Block Single, 990 lb Working Load Limit, Traveler Compatible - 29925001BK

The Lewmar Synchro Block Single (29925001BK) is a 50mm single sheave block engineered for sailboat running rigging where efficiency and durability matter. It carries a 990 lb working load limit and accommodates lines from 1/4 inch to 3/8 inch in diameter, making it suited to halyard tuning, mainsheet systems, mast foot and head blocks, and boom vangs.

The block uses a high-density Free-Spin bearing that reduces axle diameter, cutting friction and delivering up to 40% more efficiency compared to budget blocks. A self-aligning head and optimized block geometry keep the line tracking smoothly under load, while the larger sheave diameter further minimizes rope friction for smoother power transfer and reduced rope wear. The cheeks are stiff, glass fiber reinforced material that resists line wedging, and the block includes a stainless steel strap for added strength and long service life.

Design is versatile: the block switches easily between swiveling and fixed shackle configurations, and its precision-engineered shackle post gives seamless compatibility with Lewmar traveler systems. This makes the Synchro Block Single 29925001BK a practical upgrade for sailors looking to improve sail handling response without switching to a full multi-block system.

Specifications

• Brand: Lewmar
• Manufacturer Part Number: 29925001BK
• Sheave Diameter: 50 millimeters
• Working Load Limit: 990 pounds
• Line Diameter Accommodated: 1/4 inch to 3/8 inch
• Bearing Type: Free-Spin bearing
• Cheek Material: Glass fiber reinforced
• Strap Material: Stainless steel
• Shackle Configuration: Switchable between swiveling and fixed
• Traveler Compatibility: Compatible with Lewmar traveler systems
• Weight: 0.9 pounds
• Category: Sailboat Blocks

Frequently Asked Questions

What is the working load limit of the Lewmar Synchro Block Single 29925001BK? The Lewmar Synchro Block Single 29925001BK has a working load limit of 990 pounds.

What line sizes fit this block? The 29925001BK accommodates line diameters from 1/4 inch to 3/8 inch.

What sheave size does this block use? It uses a 50 millimeter sheave, which pairs with its Free-Spin bearing to reduce friction during operation.

Can the shackle be changed from swiveling to fixed? Yes, the Lewmar Synchro Block Single is designed to switch easily between swiveling and fixed shackle configurations.

Is this block compatible with Lewmar traveler systems? Yes, the 29925001BK has a precision-engineered shackle post for seamless compatibility with Lewmar traveler systems.

What is the block's construction material? The cheeks are stiff, glass fiber reinforced material that resists lines wedging, and the block includes a stainless steel strap for added strength.

How much does the Lewmar 29925001BK weigh? This block weighs 0.9 pounds.

What sailing applications is this block used for? The Synchro Block Single is suited to halyard tuning, mainsheet systems, mast foot and head blocks, and boom vangs.

Why does this block reduce friction compared to standard blocks? The high-density Free-Spin bearing reduces axle diameter and, combined with optimized block geometry and a self-aligning head, delivers up to 40% more efficiency than budget blocks.

Does the sheave diameter affect performance? Yes, the 50 millimeter sheave on the 29925001BK is sized larger to minimize rope friction and support smoother power transfer with reduced rope wear.

Is the Lewmar Synchro Block Single a single or double sheave block? The 29925001BK is a single sheave block, as indicated by its Synchro Block Single designation.