SKX013 Diver 38 Black [ULTRA THIN EDITION]

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 case body, bezel + ceramic insert (pre-fitted), and your chosen caseback + crystal. That's the foundation. Everything below is what you'll add to make a functioning, wrist-ready watch.

The 5 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. Crown — five SKX-style options. Pick a style that matches the watch's character.
   (Required to add to cart. Selected from the dropdown above on this page.)
   Browse compatible crowns
3. 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).
4. Hands — paired with your dial. Most modders match lume colour across both hands and dial markers (BGW9 white-blue, C3 green, etc.).
5. 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) — Lucius Atelier oyster, jubilee, president, GS, Seikonaut, Settimo, or more designs, plus custom shell cordovan / full-grain cowhide leather straps.
2. Decorated bridge + rotor (only visible with sapphire caseback) — replace the stock NH movement bridge and rotor with our Côtes de Genève decorated set, viewable through the sapphire caseback. Note: our bridges fit only our rotors (not OEM Seiko rotors), so they're chosen as a pair. Recommended for experienced modders only — or tick Assemble Watch below and we'll handle it.

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, crown alignment, caseback press, function check, and decorated bridge + rotor installation if you've added those.

Heads up: assembled watches require 3–5 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 (with pre-installed flat sapphire crystal — cyclops or no cyclops, per selection)
2. 1x Bezel + Black Ceramic Insert (pre-fitted, pre-aligned, with BGW9 Grade A lume pip)
3. 1x NH Caseback (Ultra Thin Solid / Thick Solid / Sapphire, per selection)

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

Why are the bezel and insert exclusive to this case?
To achieve this thinness profile, we re-engineered the case body from scratch — including the internal bezel-seating geometry. As a result, our bezel and ceramic insert are dimensionally unique. Standard SKX bezels and inserts will not fit this case, and ours will not fit a stock SKX. They ship pre-fitted and pre-aligned at our workshop. They can be removed by a watchmaker, but replacement parts will need to come from us.

Should I choose the normal or the ultra thin chapter ring?
The choice depends on your dial, not the case — both sizes fit this 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.

Does this case need a chapter ring?
Yes. The SKX013 Diver 38 [Ultra Thin Edition] 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.

Which caseback should I choose?
The Ultra Thin Solid caseback (10.86mm, 100m WR) is the headline build — this is the case at its thinnest. Choose Thick Solid (11.36mm, 200m WR) if you actually plan to take the watch diving. Choose Sapphire (11.86mm, 100m WR) if you want to display the NH movement and rotor through the back. All three pair with either cyclops or no-cyclops crystal.

Cyclops or no cyclops — and which movement do I need?
The cyclops is a magnifier lens fused to the front sapphire crystal, sitting over the date window at the 3 o'clock position. Choose cyclops only if you're using an NH35 movement — NH35 is the only NH variant in our compatible list with a date complication. NH36 has day+date, NH38 has no date, NH70/71/72 are skeletonized variants. If you pick cyclops with the wrong movement, you'll have a magnifier over a blank dial position. Choose no cyclops for any other NH movement, or simply for a cleaner crystal profile.

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 this Ultra Thin case, only Type M will fit. Confirm your movement type before ordering.

Will SKX007 dials fit?
Any 28.5mm dial will fit, but stock SKX007 dials may seat differently because the original SKX007 has a 4 o'clock crown position with offset dial feet, while our case is designed for 3 o'clock dial feet.

When do pre-orders ship?
Pre-orders are targeting a 15 July 2026 ship date. Production timelines can shift slightly depending on supplier and QC schedules — we'll email all pre-order customers immediately if anything changes. After launch, the 30% pre-order discount ends and is not repeated.

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)