What to Know About Modding the Seiko 5 Sports SSK GMT Watch

So Seiko recently released the Seiko 5 Sports SSK GMT watches, and watch modders are all asking themselves if the watch is moddable. Well, one thing’s for sure: they’re incredibly popular. But, of course, can they be modded? Well, the answer is a resounding yes!

If you are interested in modding your Seiko 5 Sports SSK GMT watch, here’s what you need to know:

Modding with the Movement

Now, the first part of the watch, and one of the major ones, we want to tackle is the movement. The watch uses Seiko’s newest movement, called the NH34A/4R34. It is a budget calibre that can tell the time in another time zone. For that fact, it was so popular that it sold out quickly after the first few days it was released.

That said, the NH34 movement is quite similar to the NH35 in both construction and appearance. And, from this, you might be wondering if you can mod the NH34. Well, since they’re mainly the same as the NH34, you can fit the movement in cases that are built for the NH35! The only concern you may have is the wider and taller hand post that the NH34 has to accommodate for the 24h hand. This may cause the second hand to bump the crystal, but you can solve this by switching the crystal to a double-dome one.

Another concern is the wider hole diameter it needs for the watch. Watches that work with the NH35 will need to have the hole widened just a bit. You need to be careful, though, as a gap too big can leave an ugly look on your watch.

Modding the Watch’s Appearance

So, what about the look? Can you mod it? Of course! You can change just about anything, but there are things to keep in mind.

For the case backs, keep in mind that the watch does not accept SKX007 case backs. However, it works with NH-style case backs. Just make sure to keep your OEM caseback gasket because aftermarket ones aren’t yet known to be compatible.

As for the crown, you can swap it with the 5KX crown. That’s because the new watch uses a push-pull crown. With the dial, you can replace it with other 28.5mm dials from Seiko. Just remember the inner hole we’ve talked about, where you’ll need to widen it a bit.

With the bracelets, ones that worked with the SKX007 watches may also work with this watch. However, keep your OEM skinny bar springs, as the lug holes on the original watch don’t accept the bigger spring bars.

Finally, SKX sapphire crystals work well on the new watches. However, remember to keep your gasket until at least new SSK-compatible gaskets show up.


All in all, that’s what you can do with the new Seiko 5 Sports SSK GMT watches. These watches offer amazing features for their price, and for the watch-modding world, these are exciting watches to mod. So, if you have an SSK watch you want to mod, keep what we’ve shared with you in mind today. That way, you can enjoy the modding process of the SSK without too much trouble.

Seiko Mods designs and manufactures various custom mod parts for Seiko watches. If you are looking for Seiko 5 mods, check out what we offer!

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