Top Seiko Mod Movements for Custom Watch Builds – Complete Guide 2025

If you’re diving into the world of watch customisation, choosing the right Seiko mod movement is one of the most important decisions you’ll make. Whether you’re building your first custom piece or upgrading an existing model, the movement—often referred to as the watch’s engine—is what drives both functionality and user experience.

In this guide, we’ll explore the top Seiko NH movements used in modding, comparing features, use cases, and why each one might be the perfect fit for your next Seiko Mod. More information on Seiko mod movements can be found here.

---

Seiko NH35 – The Best All-Around Seiko Mod Movement

The NH35 movement is arguably the most widely used movement in the Seiko modding scene—and for good reason.

Key Features:

Why Modders Love It:

The NH35 is known as a “workhorse” for its rock-solid reliability and ease of use. It’s also incredibly beginner-friendly, compatible with a huge variety of aftermarket parts (cases, dials, hands), and budget-friendly.

If you’re building a clean daily-wear watch with minimal complications, the NH35 offers everything you need—and nothing you don’t.

👉 Pro Tip: Choose between a black or white date wheel to better match your dial design and check out after market options in varying colours.

---

Seiko NH36 – Best for Day-Date Seiko Mod Movement

Looking for a little more functionality? The Seiko NH36 builds on the NH35’s strengths and adds a day display alongside the date.

Key Features:

Why It’s Popular:

The NH36 is perfect for modders who want a more informative dial layout or a vintage Seiko SKX style build. It’s equally robust and maintains the same level of accuracy and customisation potential as the NH35.

👉 Modding Tip: Go for a Kanji daywheel for a unique, Japan-inspired aesthetic.

---

Seiko NH34 – Best GMT Seiko Mod Movement

The NH34 adds something extra—GMT functionality, which allows you to track a second time zone. This makes it ideal for travel watches or builds with a more complex dial design.

Key Features:

Who It’s For:

Modders building travel-themed watches, pilot-style builds, or anyone who loves a technical timepiece with added utility. The NH34 is a bit more advanced, but it adds serious value and function to your custom watch.

If you are thinking about building a custom GMT watch check out our Vintage GMT Step by Step guide, this will give you all the information you need to assemble your own GMT watch.

---

Seiko NH70/71/72– Skeleton Seiko Mod Movement

If your goal is to build a watch that turns heads, look no further than the NH70 and NH71. These are open-heart skeleton movements, meaning the internal mechanics are visible from the front of the watch.

Key Features:

Ideal Use:

Perfect for dress watches or custom builds where aesthetic appeal is the star. The NH70 is typically silver-toned, while the NH71 / NH72 feature black or gold-accented finishes—great for colour coordination. These movements could be

---

Seiko NH38 – The Clean Open-Heart Alternative

If you’re a fan of skeleton or open-heart designs but prefer a clean, no-date look, the Seiko NH38 is an ideal choice. While less well-known than the NH70 and NH71, the NH38 is gaining popularity among modders who want mechanical beauty without added complications.

Key Features:

---

Why Choose the NH38?

Unlike the NH70 and NH71, which often come with full “skeletonisation” and elaborate dial cutouts, the NH38 offers a more refined take on showcasing the movement. It typically features a single open-heart window on the dial (around the 9 o’clock position), allowing a peek into the movement without overwhelming the design.

For modders, this is a huge plus—it means:

• Greater flexibility in dial designs
• No need to hide or mask unused date/day windows
• Clean symmetry and a modern aesthetic

---

🆚 NH38 vs NH70/71/72

Feature	NH38	NH70 / NH71
Date/Day	❌ None	❌ None
Skeleton Dial	Partial (open-heart)	Full skeleton
Design Style	Minimalist, clean	Showpiece, ornate
Ideal Use	Elegant open-heart mod	Bold statement mod

Ideal For:

• Dress watches with mechanical flair
• Minimalist mods that avoid clutter
• Custom builds that need open-heart appeal without overcomplicating the dial

---

---

Choosing the Right Seiko NH Movement for Your Mod

There’s no one-size-fits-all answer when it comes to Seiko mod movements. Each NH series movement serves a different purpose depending on your build goals:

Compatibility Tip:

All of the Seiko mod movements are essentially the same. These movements aka ‘calibres’ are built on the ‘base calibre’ 7S26, the movement found in legendary SKX. So which ever you choose for your mod it will fit the same cases, hands, and crowns—making it drop-in ready for most Seiko mod builds. The one limitation is the NH34 where the hand height will sit a little higher so consideration must be given to the case choice.

Movement	Best For	Key Feature
NH35	Beginners / Daily Wear	Reliable, no-frills modding
NH36	Classic Builds	Day-Date complication
NH34	Travel or GMT Watches	Second time zone functionality
NH38 – NH70 – NH71	Visual Statement Pieces	Skeleton /open-heart design

Ask yourself:

• Do I want functionality, like day or GMT?
• Is aesthetic design my top priority?
• Am I creating a rugged field watch or a sleek dress watch?

Once you’ve answered these, your ideal Seiko mod movement becomes much easier to identify.

---

Final Thoughts: What’s the Best Seiko Mod Movement?

The best movement for Seiko modding really depends on your vision. The NH35 is the most versatile and beginner-friendly. The NH36 adds day-date functionality. The NH34 is perfect for GMT lovers. And if you want mechanical beauty on display, the NH38, NH70, NH71 or NH72 is unbeatable.

At the end of the day, the best Seiko movement for modding is the one that offer the most option on parts to bring your ideas to life.

If you are looking to up your game with a more accurate Seiko mod movement akin to a chronometre, Check out the Seiko NE range of Movements again built on the base calibre 7S26.