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Allen Brothers 20MM Dynamic Back To Back

Note: Some prices may reflect updates due to international tariffs. Learn the latest about tariffs

Tariff Updates

We are observing how the tariffs are behaving. Lots of our products are imported from Europe and some of the manufacturers are not providing heads up about price increases. We will do everything in our power to hold the best prices, but please consider that in these uncertain times we may be forced to increase the prices without previous notification.

We really appreciate your understanding and look forward to working with you.

What does this mean for you?

  • Some imported products may show a higher price than usual.
  • Prices may change as shipping rates adjust globally.
  • We are committed to providing the best possible pricing and transparency at all times.

How we’re handling it:

  • We only adjust prices when absolutely necessary.
  • We continuously monitor shipping rates and update pricing accordingly.
  • We’ll clearly notify you if a product is affected by tariffs.

Questions? Feel free to contact our team for any clarification or assistance.

Updated: April 2025

MSRP: $33.21
$31.80
(You save $1.41 )
(1 review) Write a Review
SKU:
ALNA2028
Availability:
Please contact us to confirm availability or discuss item replacements. Please note that certain products may have an estimated arrival time of 30 days and are not available for expedited shipping.
Weight:
0.04 LBS
Shipping:
Calculated at Checkout.
Size:
20 mm

20mm Back To Back Dynamic Block.

The sheaves face opposite directions to allow two control lines to run at a maximum of 180 degrees to each other. Held together with a strong stainless steel side strap and nylon mouldings ensures the block will not separate even under two very high opposing loads.

The strength of the design lends itself to be tied around the middle in the slight V shape, meaning it can be used in applications such as triangle backstay systems found on sports boats.

One of the more popular applications is in a dual pole and spinnaker launcher system such as the system commonly found on a 49er.

Bearings - Dynamic Blocks feature our patented bearing system which uses twin rows of stainless-steel ball bearings running on a stainless-steel rail. This provides a superior load-carrying ability and longevity when compared to other bearing systems which run on a plastic rail.

Becket - Our 20 & 30mm blocks offer a large central rivet which not only reduces the overall weight but also offers a rope friendly attachment, perfect as a tie-off point when being used in a cascade system.

Technical Description
2 5/64 in
52.8 mm
15/64 in
6 mm
1190.5 lb
540 Kg
253.53 lb
115 Kg
0.70 oz
20 g
-
Stainless Steel

1 Review Hide Reviews Show Reviews

  • 3
    Double Block

    Posted by Alan on Jul 26th 2024

    It is actually too small for the application. The size was unclear when I ordered it. I am hoping descriptions and dimensions can be improved on. What dimension of the block is 20mm? I'd like to know what size line fits in the blocks, and what is the distance from shive to shive?