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Build Your Own Visually

SKX013 Diver 38 Black Ultra Thin Edition — side profile showing 10.86mm ultra-thin case thickness

Ultra Thin Edition
Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

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  • SKX013 Diver 38 Black Ultra Thin Edition — side profile showing 10.86mm ultra-thin case thickness

    Ultra Thin Edition
  • Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

    Seikonaut
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    Home / SEIKO SKX013 Mod Parts / SKX Sapphire Caseback - Silver
    SKX Sapphire Caseback - Silver - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

    SKX Sapphire Caseback - Silver

    $45 SGD

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    The Exhibition Back. Sapphire. For SKX builds.

    The sapphire caseback turns the back of your watch into a window — the NH movement, the rotor swinging, the whole caliber on display. A sapphire crystal set into a 316L stainless steel ring, made for SKX cases running Seiko NH movements.

    Water pressure tested to 200m — properly installed and tightened, it's Diver's-200m rated. Running a decorated rotor or bridge? This is the back that makes them worth it.

    Show the movement.
    The back worth turning the watch over for.

    Sapphire window.
    A sapphire crystal set into the steel ring — the movement stays on display.

    316L, polished edge.
    Machined stainless steel carrying the sapphire — see Specs for the detail.

    200m rated.
    Water pressure tested to 200m, properly installed and tightened.

    Fits SKX + NH.
    All SKX cases running Seiko NH movements — SKX007 and SKX013 families alike.

    Heads up — fit & install

    Fits all SKX cases running Seiko NH movements. Fitted a decorated rotor or bridge? The sapphire back is what lets you see them.

    New to this? Seiko Modding: The Complete Build Guide walks through the whole build.

    • Specs

      1. Quality Swiss Production Quality, ISO 9001 Certified
      2. Material 316L Stainless Steel
      3. Surface Finish Polished Edge
      4. Crystal Sapphire
      5. Thickness 1.8mm
      6. Water Resistant 200m
      7. Fit SKX Cases using NH movement
      1. 1x Caseback

      All photos of watches with modification parts are for illustration purposes only and are not included with the purchase.

    • Fits all SKX cases running Seiko NH movements.

      Pairs with:

      1. Rotors & Bridges
      2. Watch Cases
      1. Seiko Modding: The Complete Build Guide (2026)

    Questions, Answered

    Everything worth knowing before you build.

    What's the difference between a solid and a sapphire caseback?

    A solid caseback is a plain steel cover — the cleanest look, and the standard version is water pressure tested to 200m when properly installed. A sapphire caseback sets a sapphire crystal into the steel ring, turning the back into a window on the movement. If you've fitted a decorated rotor or bridge, the sapphire back is what lets you see it.

    Will these casebacks fit my SKX007 or SKX013?

    Yes — they're designed for SKX cases, covering both the SKX007 family (7S26-0020) and the SKX013 family (7S26-0030), on builds running Seiko NH movements.

    Why choose the slim solid caseback?

    It cuts the caseback's thickness from 1.3mm to 0.75mm, which lowers the finished watch's profile on the wrist. The trade-off is water resistance: the slim version is pressure tested to 100m, against 200m for the standard solid caseback.

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