Watch Case for seiko modding

Seiko Mod Cases — Royal Oak, Nautilus, Aquanaut, Petrichor

Start with the perfect case

Build your Seiko mod around a case that defines the look and the fit. From angular Royal Oak and elegant Nautilus to sporty Aquanaut and minimalist Petrichor, our cases are engineered for NH35/NH36 compatibility with clear fit notes for crystals, crowns, bezels, and bracelets.

20 products

FAQs — Seiko Mod Cases

Which movements fit these cases?
All listed cases target NH35/NH36 by default. Some skeleton/integrated builds may also accept NH7x—check each product’s fit notes.
What case sizes are available?
Common sizes include 37 mm and 41 mm for Royal Oak-style, 39–41 mm for Aquanaut-style, ~40–42 mm for Nautilus-style, and 42 mm for SKX/5KX-inspired cases. See the product specs for exact dimensions and wrist presence.
Which dial size do I need (28.5 vs 30.8 mm)?
SKX/5KX and many 37 mm builds use 28.5 mm dials. Larger windows like Royal Oak 41 mm or Aquanaut 39–41 mm often use 30.8 mm. Always match the case’s dial window spec.
Are crystals and bezels interchangeable between styles?
Usually no. Integrated-style cases (Royal Oak/Nautilus) use specific crystal heights/profiles and bezel geometries. Diver-style (SKX/5KX) cases support standard bezel/insert formats. Check each listing for compatible crystal profile and bezel type.
Integrated bracelet vs standard lugs—what’s the difference?
Integrated cases (Royal Oak/Nautilus) are designed for a matching bracelet and won’t accept standard spring-bar straps. Standard lugs (e.g., SKX/5KX, some Aquanaut) accept most 20/22 mm straps and bracelets—verify lug width in the specs.
Do crowns and stems come included?
Many cases ship with a matching crown/tube. Stems are cut to length for your movement during assembly. Review the listing to confirm crown type (screw-down/push-pull) and water-resistance notes.
Water resistance—what should I expect?
Ratings vary by case, crystal, gasket fit, and assembly quality. If you need swimming-safe builds, choose cases with stated WR ratings and assemble/test with proper gaskets and torque. DIY mods should always be pressure-tested if water use is intended.