Sinn watches are known for their toughness and simple designs that are made to be used by professionals. Some may say they are one of the last purpose-built diver's watches.

While many watch companies follow trends in the market, Sinn has kept their business model solid in the face of a changing market for watches. Sinn is famous for crafting dive watches made from German submarine steel, and using rock-solid Swiss movements.

The EZM is perhaps the Sinn's best-seller, but the U1 also has a massive following in the watch community. In fact, many Seiko modders love to take the Seiko SKX, and make it an homage to the iconic design of the Sinn U1.


Sinn U1: Where Did The U1 Come From?

Isn't it just majestic? Source: Sinn


In 1961 Sinn made its first move into the world of watches. Sinn’s orientation in its early years was pilot watches – but this era also gave birth to design ideals that would eventually lead to the U1 in 2005.

The company’s vision was to combine advanced technologies and materials in its products, which are not only robust and durable, but also stand out for their high performance and variety of uses.

In 2005, Sinn introduced a new diving watch developed by their in-house engineering team: the Sinn U1. One of the major highlights of the U1 model is the submarine steel case it uses and its unique design.

Many modern watches use luxury materials – well – because they are expensive (think the Rolex ceramic bezel insert that is shot with gold particles) but with the U1, the watch is made to be used, and used by professionals.


Sinn U1 Features

The U1 model features a water-resistance standard that meets German technical diving standards, and has been tested and certified according to European standards.


It's overengineered to be a desk diver, but who cares when it looks this great? Source: Reddit


While the actual water resistance will vary by model (there are a few variations out there), the base U1's have 1000m of water resistance.

The bezel and bezel insert design is also an interesting highlight. Rotating the bezel requires 2 pressing and rotating operations, ensuring that the bezel is not rotated by unwanted accidental impact.

When it comes to Sinn, the company makes no mistakes on how the case is designed and built. The case and crown are made from German submarine steel, which is salt water resistant and antimagnetic – two traits that any professional would want to have on their diver’s watch.

The Sinn U1 is 44mm in diameter and 14.3mm thick. It has 22mm lugs, and despite being a larger watch, it wears well in its native environment – underwater.


Sure, they designed the U1 to be legible, but it also ended up attention-grabbing. Source: Rolex Forums / uvalaw2005


The U1 uses an oversized crown at the 4 o'clock position, which makes the watch easier to wear, or adjust the time when it is on wrist. Besides the crown, the case is very basic, and has a smooth, matte finish.

Newer versions are surface hardened with Tegiment technology, giving the case a higher hardness and probably making them less prone to scratching.

The dial of the U1 has a matte black background and uses a simple design that is easy to read. The hands that Sinn uses on the U1 are interesting, and allow the time to be readable at a glance, and also specifically as the hands have small protrusions at the very end that allow exact readings.


A very inspiring watch indeed, and now easy to recreate for a homage mod. Source: Sinn


It is impossible to overlook the second hand on a Sinn U1 – it has a massive red square near the end – and can be read in almost any conditions.

Overall the Sinn U1 is notable for what it is – a tough as nails diver's watch that is easy to read, and is actually made to be used daily in the harshest ocean environments. A Rolex Submariner can be used for diving – but a Sinn U1 won't be happy living on land!


The SKX U1 Mod: Parts For U1 Modifications

The Seiko SKX is infinitely moddable and it actually lends itself to the clean designs that Sinn used in the U1. While very few of the stock parts on an SXK will remain on a U1 mod, making your SKX into a U1 inspired diver is easy with NamokiMODS.



The dial on the Sinn U1 is basic, but very unique. Some people call it a Lego Style Dial!

It has small white hour markers on a deep black background, and our U1 homage dial is a perfect fit for the Seiko SKX case.



Diving watches have a simple, clear, and high-contrast design, and the Sinn U1 is no exception. We used C3 Super-LumiNova® Lume to make the hour markers on our U1 homage dial shine, like any diver's watch should.

When you use NamokiMODS parts to do Seiko mods, you will be getting parts that are at least as good as OEM, if not better – the lume included.

We designed our U1 homage dial with a date window, making it correct for the NH35, which gives you the date, and not the day complication.

If you want to make your U1 mod ever more personalized, check out our NH35 with black date wheel, or just use a standard NH35 if you like the white date wheel!



The hands that Sinn designed for the U1 stand out on any watch dial.



We know that our clients love options, so we created both a black and orange version of the iconic U1 hand set. The overall design of the hands is the same, but we changed the color so that Seiko modders have more style options.

Unlike other watches that have a bit more flexibility when it comes to mixing and matching dials and hands, a Sinn U1 homage should have matched dial and hands, and pull off the look perfectly.


Bezel and Bezel Insert

The Sinn U1 has a distinctive bezel insert, and much like the hands, we have a few options for you to choose from. While most people associate a steel bezel with the Sinn U1, we also crafted a black version that you can use to make something a little different.

When it comes to the bezel – we have a few great options for you to choose from. Many people try the mod first with the stock SKX bezel and crystal, but our LX bezel, or MM300 bezel might be a closer match to the chunky U1 bezel.

We stock loads of skx007 bezel insert and skx007 sapphire crystal options, so you can upgrade your stock SKX into whatever you want. Or – if you want to start from scratch, our parts catalog has everything you need to build watches for years to come!


Modding it Right With NamokiMODS

Let's be honest – if you are into Seiko mods, you like making something a little different. At NamokiMODS we know you want the best aftermarket parts in the world, which is why we put quality and variety first.

If you want to mod a plain steel SKX case – no problem, we have loads of parts for you. But if you want to take your Seiko diver mod to the next level – take a look at some of our custom cases that really give you a lot of modding options.



For example, our matte black MM300 case would make an amazing base for a black U1 custom mod, and it is totally compatible with SKX parts so you can mix and match to make whatever design you want.

We stock loads of aftermarket Seiko SKX mod parts, and you can create just about any kind of custom watch imaginable. If you want a totally customized diver watch – we can help you – but we also have other kinds of styles as well.

For more information about what we offer – please take a look through our extensive website. At NamokiMODS – Seiko mods come first!

July 19, 2021 — Jeremiah A


Catalin said:

Sinn U1 hands are not orange and white but red and white. Are you going to produce one red set?

Tony bertone said:

Hi. The u1 style look orange. However rhe u1 homage dial looks red. I was hoping they would be the same color. Can someone comment if they match? Thanks

Andrew Burns said:

I want to build a 62MAS watch with your parts. I love my U1 so I want to recreate that look using the timeless simplicity of the 62MAS case. Will your U1 dial work? It is 28.5mm? Looking at my U1 it doesn’t look like Sinn uses a chapter ring. I’d want to use a Seiko NH35 movement so your U1 hands should work.

Anyway, any guidance you have is appreciated.

Your website is A++. Props!


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