Lewmar 50mm Synchro Double Block with Becket – Black | 29925005BK
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Lewmar 50mm Synchro Double Block with Becket – Black
The Lewmar Synchro 50mm Double Block with Becket is a compact, efficient block designed for sailing control systems where mechanical advantage and a secure line termination point are both needed. The twin-sheave configuration delivers smooth load handling, while the integrated becket opens up compact purchase, cascade, and fine-tuning arrangements that a standard double block can’t accommodate.
Lewmar’s Synchro design combines a high-density free-spin bearing, stainless steel strap, glass-fiber reinforced cheeks, and an adjustable swivel-locking system for dependable performance across the full range of running-rigging applications.
Specifications
- Part Number: 29925005BK
- Sheave Diameter: 50 mm
- Configuration: Double sheave with integrated becket
- Recommended Line Diameter: 1/4" (6 mm)
- Maximum Line Diameter: 3/8" (10 mm)
- Working Load Limit: 990 lbs (450 kg)
- Weight: 5.77 oz (164 g)
- Shackle Post Diameter: 5/16" (7.9 mm)
- Shackle Pin Diameter: 5/32" (4 mm)
- Finish: Black composite
- Barcode / UPC: 743683220159
Features
- Double-sheave configuration with integrated becket for versatile purchase arrangements
- High-density free-spin bearing — reduces friction for efficient line handling
- Glass-fiber reinforced cheeks — help prevent line wedging under load
- Stainless steel strap for strength and corrosion resistance
- Swivel mechanism configurable for fixed or rotating operation
- Patented shackle post lock for secure, easy attachment
Compatible Applications
- Mainsheet systems requiring compact double-block purchase
- Boom vangs and kicker systems
- Outhaul and Genoa control systems
- Running backstays
- Halyard tuning and fine-adjustment arrangements
- Cascade purchase systems on performance and cruising sailboats
Fitment Note
Confirm the 50 mm sheave size, rope diameter (1/4"–3/8"), working load, shackle dimensions, becket arrangement, and available installation space before replacing or upgrading an existing block. Running-rigging loads vary substantially by vessel and application.
Related Products
- Lewmar 60mm Synchro Double Block with Becket – Black
- Lewmar 72mm Synchro Double Block with Becket – Black
- Lewmar 50mm Synchro Triple Block – Black
- Lewmar 50mm Synchro Double Block – Black (without Becket)
- Lewmar 60mm Synchro Triple Block with Becket & Cam – Black
Parts Desk Insights
Best use case: This block is the right call when you need a compact double-block with a built-in termination point — particularly for mainsheet and vang purchase systems where the becket anchors the standing end of the tackle. It’s well suited to smaller performance boats and daysailers where the 50 mm sheave and 450 kg WLL match the load range.
When selecting a replacement or upgrade, focus on the three numbers that matter: 50 mm sheave, 1/4"–3/8" rope range, and 990 lb working load. Matching those to your existing purchase system is more reliable than choosing by appearance alone. If your loads or line sizes are larger, step up to the 60mm or 72mm version.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.