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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

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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 / All Products / Seikonaut 38mm — Ultra Thin Titanium Watch Case
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

    Seikonaut 38mm — Ultra Thin Titanium Watch Case

    $219 SGD
    Worldwide
    Delivery         Express
    2–4 Days         Replies In
    1 Day         30-Day
    Returns

    Seikonaut 38mm Ultra Thin Titanium Watch Case in featherlight Grade 4 titanium

    Featherlight Strength. Reborn Ultra Thin. Built in Titanium.

    Introducing the Seikonaut 38mm Titanium, part of our Ultra Thin Edition series — an iconic reinterpretation of a legendary sports-luxury silhouette, now engineered to be among the thinnest NH-compatible watch cases ever made, and built entirely in Grade 4 titanium.

    The Seikonaut aesthetic — defined by its angular case geometry, sculpted flanks, and sporty elegance — has achieved cult status in the watch modding world. Coveted for its versatility and bold wrist presence, it blends refined design with everyday wearability.

    While the bezel measures 38mm, the case tells a bigger story. Factoring in the flared side flanks, the full case width reaches 42mm, and with the included 7mm coin-edge crown, approximately 44mm. A commanding presence that still wears balanced — bold, refined, and at home on any wrist size.

    Built around your choices. This is a case to build on. You choose the chapter ring, the dial, the hands and the movement — and because every Lucius Atelier case shares the same 28.5mm dial standard, the parts you'd buy for a Bauhaus 33 or an Explorer 36 fit the Seikonaut too. One parts ecosystem, one set of tolerances. Two things are already done for you: the 7mm titanium coin-edge crown is included — no crown to source — and the flat sapphire crystal ships pre-installed and aligned at our workshop, so there's no crystal-pressing at your bench.

    Wears 38, lives bigger.
    Bezel diameter 38mm, full case width 42mm with the flared flanks, around 44mm with the 7mm crown. Lug-to-lug 47mm, lug width 20mm. A bold sports-luxury silhouette on a compact canvas.

    Genuinely thin.
    10.0mm with the solid caseback. The engineering behind that number: a standard NH movement is 7.59mm tall on its own — which leaves barely 2.4mm for the crystal, case walls, and hand clearance combined. Tight engineering, in titanium.

    Featherlight by design.
    Just 29 grams on the case alone — over 40% lighter than the 316L steel Seikonaut at 49.4 grams. Grade 4 titanium is harder than steel, naturally corrosion-resistant, and carries its own distinctive subtle grey tone. A dramatic reduction in wrist fatigue, with no loss of strength.

    Bracelet, your call.
    The 20mm lug takes any standard 20mm strap or bracelet. We recommend our Seikonaut Titanium Bracelet for a full featherlight titanium build — but every other Lucius Atelier bracelet fits too.

    Caseback Total Thickness Water Resistance Best for
    Solid Titanium · INCLUDED 10.0mm 100m / 10 ATM The thinnest profile — featherlight daily wear

    The Titanium Seikonaut ships with a solid titanium caseback included — the case at its slimmest, at just 10.0mm.

    Heads up — sold separately

    Chapter ring. This case requires a SKX013-spec chapter ring to seat the dial correctly — without it, the dial sits too low and hands won't clear. The case fits both normal and ultra thin chapter rings; the choice depends on your dial, not the case. If your dial has applied (raised) indices, choose ultra thin for clearance. If flat-printed, either works. When in doubt, ultra thin is the safer default. Browse compatible chapter rings .

    The crown, caseback and sapphire crystal are all included with this case. You only need a dial, hands, chapter ring and movement to complete the watch.

    For experienced modders only — TYPE M movements only

    This case fits TYPE M versions of NH35, NH36, NH38, NH70, NH71, NH72 only. TYPE L will NOT fit. Due to tight clearance between hands and sapphire, this case is recommended only for professional watchmakers and experienced modders.

    • Dimensions

      1. Bezel Diameter 38mm
      2. Case Width (with flanks) 42mm
      3. Case Width (with crown) 44mm
      4. Case Thickness 10.0mm (Solid Caseback)
      5. Case Weight 29g (Titanium) vs 49.4g (316L Steel) — over 40% lighter
      6. Lug to Lug 47mm
      7. Lug Width 20mm

      Materials & Finish

      1. Quality Swiss Production Quality, ISO 9001 Certified
      2. Material Grade 4 Titanium — case, crown, caseback
      3. Case Finishing Brushed
      4. Crown 7mm coin-edge, screw-down (titanium, included)
      5. Crystal Flat Sapphire with clear anti-reflective coating
      6. Crystal Size 29.5mm x 1mm

      Compatibility

      1. Movements TYPE M: NH35, NH36, NH38, NH70, NH71, NH72
      2. Dials 28.5mm
      3. Chapter Rings SKX013-spec (required, sold separately)
      4. Hands NH movement compatible
      5. Crowns 7mm titanium coin-edge (included)
      6. Bracelets 20mm lug — Seikonaut Titanium Bracelet recommended for a full titanium build; fits all Lucius Atelier bracelets and any standard 20mm strap

      Water Resistance

      1. Solid Caseback 100m / 10 ATM

    • New to Seiko modding? Here's everything you'll need for a complete, functioning watch — in the order you'd actually assemble it.

      What's already in this purchase:

      The titanium case body, the 7mm titanium coin-edge crown (included), the solid titanium caseback, and the pre-installed flat sapphire crystal. That's a near-complete watch — you only need to add what goes on the dial side.

      The 4 parts you'll need for a complete watch:

      1. Chapter ring — required first. The chapter ring seats the dial at the correct height; without it, the dial sits too low and the hands won't clear.
        (SKX013-spec — sold on a separate page. See the "sold separately" panel above for normal vs ultra thin guidance.)
        Browse compatible chapter rings
      2. Dial (28.5mm) — the face of the watch. The biggest aesthetic choice you'll make. Match it to your chosen movement (date / day+date / no-date dial).
      3. Hands — paired with your dial. Most modders match lume colour across both hands and dial markers (BGW9 white-blue, C3 green, etc.).
      4. Movement — NH35 (date), NH36 (day+date), NH38 (no date), or source your own. The movement is the engine of the watch.

      Optional finishing touches:

      1. Bracelet or strap (20mm lug) — we recommend our Seikonaut Titanium Bracelet for a full titanium build, plus custom shell cordovan / full-grain cowhide leather straps.

      Want it built for you?

      Tick the Assemble Watch (+SGD $50) option above on this page and we'll handle the full build in our Singapore workshop — case fitting, movement seating, caseback press, and function check.

      Heads up: assembled watches require 2–5 business days of workshop time before shipping.

      Once your parts arrive, see the How To Mod tab for assembly tutorials.

      1. 1x Watch Case Body (Titanium, with pre-installed flat sapphire crystal)
      2. 1x Crown — 7mm coin-edge (Titanium, included)
      3. 1x NH Caseback — solid, non-display (Titanium)

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

      1. A Complete Guide On How To Mod Your SEIKO Watch Dial And Hands (Photos & Video)
      2. Fitting dials with four dial legs
      3. Seiko Modding: The Complete Build Guide (2026)

    Questions, Answered

    Everything worth knowing before you build.

    How light is it, really?

    Just 29 grams on the case alone — over 40% lighter than the 316L steel Seikonaut at 49.4 grams. That's the practical payoff of Grade 4 titanium over stainless steel: a dramatic reduction in wrist fatigue with no loss of strength.

    What comes in the box — do I need to buy a crown?

    No. The Titanium Seikonaut ships as a complete case: titanium case body, 7mm titanium coin-edge crown (included), solid titanium caseback, and a pre-installed flat sapphire crystal. To finish the watch you only need a dial, hands, chapter ring and movement.

    Which bracelets and straps fit?

    The Seikonaut Titanium uses a standard 20mm lug width, so it takes any 20mm strap or bracelet. We recommend the matching Seikonaut Titanium Bracelet for a full titanium build, but every other Lucius Atelier bracelet fits too — the case is a foundation, and how you finish it is yours to decide.

    Why does the case look bigger than 38mm?

    The bezel measures 38mm, but the Seikonaut's flared side flanks push the full case width to 42mm — and to around 44mm with the 7mm crown installed. It's a deliberate part of the sports-luxury silhouette: a bold wrist presence on a case that still wears balanced.

    What's the difference between Type M and Type L?

    Type M and Type L are Seiko's two factory hand-fitting versions of the NH series. Type L sits higher than Type M — about 0.4mm taller from base to second-hand pinion. Because of the tight clearance between hands and sapphire in Ultra Thin Edition cases, only Type M will fit. Confirm your movement type before ordering.

    Do I need to remove the sapphire crystal to install the chapter ring?

    No — and that's the whole point of us pre-installing the sapphire for you. The chapter ring sits on top of the dial inside the case, not under the crystal, so the crystal stays where it is throughout the build. (If you ever do need to remove the sapphire — for example, to replace it — that's a workshop job we handle for you, not an at-home step.)

    Should I choose the normal or the ultra thin chapter ring?

    The choice depends on your dial, not the case — both sizes fit every Ultra Thin Edition case. If your dial has applied (raised) indices, the ultra thin chapter ring is the better choice because its slimmer profile gives the indices clearance instead of resting on top of them. If your dial is flat-printed (no applied markers), either size works. When in doubt, the ultra thin chapter ring is the safer default because it works with both dial types.

    What is an SKX013 chapter ring and why does it matter?

    A specific size and spec used by Seiko in the SKX013 (discontinued 2019). The LA smaller-case lineup all uses this same spec, which means dozens of chapter ring designs work across every smaller case in the catalogue.

    Will SKX007 dials fit?

    Any 28.5mm dial will fit. Stock SKX007 dials may seat differently because the original SKX007 has a 4 o'clock crown position with offset dial feet, while Ultra Thin Edition cases are designed for 3 o'clock dial feet.

    Does this case need a chapter ring?

    Yes — every Ultra Thin Edition case requires an SKX013-spec chapter ring, sold separately. The chapter ring seats the dial at the correct height; without it, the dial drops and the hands will not clear properly.

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