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seaHorse | Weblock for 20 / 25mm Webbings

(14 customer reviews)

14.00 142.00

The seaHorse is the world’s first ISA 51 certified HighTech Highline Weblock. Made from a single piece of aluminium, has a versatile HollowCenterDiverter and a excellent PreTension-Ability. This WebLock also impresses with its low weight and, at the same time, the generous dimensioning, which allows comfortable handling (even with up to 8mm thick slackline webbing).



seaHorse 1.5: the best pretension-ability weblock with Double-Pin

isa approved highline aproved weblocker
ISA Certificate

According to ISA 51 Standard, the SLACKTIVITY seaHorse is a tested and certified highline double-pin weblock

The seaHorse is the most sophisticated weblock on the market, it can be used with 25mm and 20mm webbings (with spacers). The new design adds versatility, new functions, and low weight. The seaHorse is forged from a single piece of aircraft aluminium, which allows it to be really strong and lightweight.

The biggest innovation is the hollow center diverter which allows a variety of soft connections. This can be really useful when building a HangOver pulley system, attaching a regular pulley system, or attaching a rope to train for highlines in the park. We even built in some grooves that keep your soft attachments in place instead of sliding up. Note: the hollow center diverter cannot be used to anchor the seahorse.

The geometry of the SLACKTIVITY seaHorse is optimized for the most efficient pretension possible. A lot of testing with a big modular plate has led to the perfect dimensions for a HangOver pulley system. To see how to create the lightest 15:1 system on the market, you can watch the video above!

The two pins are connected with a rubber connection cord which is less likely to get entangled around the pins while tensioning the line.


  • Working Load Limit (WLL) 12kN, MBS:70kN
  • Designed for slacklines of 19mm to 20mm (20mm with spacers) and 25mm to 27mm wide
  • ball locking pin (d=11.1mm, weight-optimized) out of high alloy, stainless steel (17-4PH)
  • made from aircraft aluminium 7075-T6 in SLACKTIVITY-Green
  • hot forged from one piece
  • 36mm HollowCenterDiverter (HCD) works like a riggingplate!
  • Weight: 260g
  • tested and certified according to ISA 51standard


The seaHorse spacers make this weblock suitable for 20mm webbings. They are sold in pairs as each seaHorse requires two.

Before using this equipment, you must read and understand all instructions for Use! Check the manual (PDF) on the manuals tab. And make sure to use the anti-slippage knot as explained in the manual by every rigg!

It is important to SLACKTIVITY to pass on the necessary know-how to our customers with the material they buy. That is why we make the manuals as clear, simple and visually appealing as possible. Please have a look! If you still have any questions, we are happy to help. And check out for more information on SLACKTIVITY’s Youtube-Channel.

Check the video on how to use the seaHorse

Reviews (14)

14 reviews for seaHorse | Weblock for 20 / 25mm Webbings

  1. English


    By far my favourite weblock. Is super easy to pre-tension and to make the anti slipping knot (because of the hole in the middle). It works great with tick soft-realeses.

  2. English

    Diego Delgado Elguera (verified owner)

    Es una banana muy bien construida, y muy suave para tensar. Sin duda la volvería a comprar.

  3. English


    Very good webblock : it’s easy to feed the slack through it and you can also connect a soft-released to it (for a cleaner rig).

  4. English

    Emile (verified owner)

    Great line locker.

  5. English

    Anonymous (verified owner)


  6. English

    Anonymous (verified owner)

    Top 🙂

  7. English

    Anonymous (verified owner)

    Top gear

  8. English

    R Rioza (verified owner)

    also good

  9. English

    Rotem Cahanovitc

    Love the use of it, simple and elegant

  10. English

    Diede De Proost (verified owner)

    A pleasure to work with, awesome piece of gear!

  11. English

    Rex S (verified owner)

    I absolutely love this weblock. It is so light and having the center diverter makes both tensioning and tying off tails a breeze. From the friction divots to the hooks you can tell that this was designed by people that love slacklining. I would highly recommend.

  12. English

    Marian Gheti (verified owner)

    Works great

  13. English

    Cole Chilton (verified owner)

    No complaints. Great product!

  14. English

    Robert L. (verified owner)

    smooth as butter for buckingham tensioning systems. looks great too, especially with kingpin shackles.

Show only reviews in English (14)

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