How is this thinner than a normal SKX013 mod?

The original Seiko SKX013 measures 13mm, and a typical mod build pushes that to around 14.5mm once aftermarket parts are fitted. The SKX013 Diver 38 lands at 10.86mm with the Ultra Thin solid caseback — thinner than the original. We achieved it by re-engineering the case body from scratch, compressing every internal dimension without compromising structure.

Why are the bezel, insert, and crystal exclusive to this case?

To achieve this thinness profile, we re-engineered the case body from scratch — including the internal bezel-seating and crystal-seating geometry. As a result, our bezel, ceramic insert, and sapphire crystal are dimensionally unique. Standard SKX bezels, inserts, and crystals will not fit this case, and ours will not fit a stock SKX. They ship pre-fitted and pre-aligned at our workshop.

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 (11.76mm, 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.

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.

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 press the crystal myself?

No. The flat sapphire crystal ships pre-installed and aligned at our Singapore workshop. The chapter ring sits on top of the dial, inside the case — not under the crystal — so the crystal stays put throughout your build.

SKX013 Diver 38 [Ultra Thin Edition]

Q: 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.

Same 38mm diameter. A stock SKX013 modded to 14.5mm versus the SKX013 Diver 38 at 10.86mm — roughly 25% thinner.

The SKX013 Diver 38 is our ground-up reinterpretation of the dive-watch icon — engineered to be among the thinnest NH-compatible dive cases on the market today. 10.86mm with the Ultra Thin solid caseback. A 38mm case that wears 40 with the crown guards. The dimensions of a daily driver, the lineage of a tool watch.

Here's the thing about thinness in a dive case: it usually goes the wrong way. The original Seiko SKX013 measures 13mm — and a typical mod build, with its aftermarket bezel, insert and crystal, pushes that to around 14.5mm. Modding a diver almost always makes it thicker. We went the other direction. The SKX013 Diver 38 lands at 10.86mm — thinner than the original it takes its name from.

Getting there meant rebuilding the case body from scratch. Every internal dimension was re-engineered to compress height without compromising structure — which is why the bezel and ceramic insert are dimensionally exclusive to this case, and why we ship them pre-fitted and pre-aligned at our Singapore workshop. No fitting the rotating bezel yourself, no sticking and aligning the ceramic insert, no crystal-pressing the sapphire. For a dive build, that's the hardest, most finicky workshop time — done for you.

What we kept open is what modders actually want flexibility on: SKX-style crowns, SKX013-spec chapter rings, 28.5mm Seiko Mod dials, hands, and the NH35 / NH36 / NH38 / NH70 / NH71 / NH72 movements (Type M). The thinnest dive-style profile we could engineer, paired with the modding ecosystem you already know.

Black or green — which is right for you?

Same case, same engineering, same build options. The ceramic insert is the only difference — and it sets the whole character of the watch.

Black Ceramic Insert The original dive-watch language. Versatile, formal, timeless — it pairs with any dial and reads correctly with a suit or a t-shirt. The safe-but-never-boring choice, and the one most builds start from.
Green Ceramic Insert The modern tool-watch flex. Bolder on the wrist and harder to ignore — green is the colourway that gets the "what is that?" question. Choose it when you want the build to stand out.

Configure your build

Both colourways ship with the same options: three casebacks and two crystal choices. This is where you decide how the watch actually wears.

The caseback sets your thickness and water resistance:

Caseback	Total thickness	Water resistance	Best for
Ultra Thin Solid	10.86mm	100m / 10 ATM	Daily wear — the thinnest profile, the headline build
Thick Solid	11.36mm	200m / 20 ATM	Modders who actually take it diving
Sapphire	11.76mm	100m / 10 ATM	Movement display — show off the rotor

The Ultra Thin Solid caseback is the headline build — the case at its slimmest. The other two trade a little height for a full 200m dive rating or a view of the movement.

The crystal is a simpler choice — cyclops or no-cyclops — but it depends on your movement. The cyclops is a magnifier lens fused over the date window at 3 o'clock, so it only makes sense with an NH35 (the date movement). NH36 is day+date, NH38 has no date, and the NH70/71/72 are skeletonized — for any of those, or simply for a cleaner crystal, choose no-cyclops.

Live · Community Build Data

What modders actually choose

Every SKX013 Diver 38 build, tallied.

Ceramic Bezel Black 81%Green 19%

Black is the timeless default — where most builds start. Green is the quiet flex, the one that gets the “what is that?”

Caseback Ultra Thin 79%Thick 10%Sapphire 11%

Ultra Thin is the runaway favourite — the slimmest, headline build. Thick trades a little height for a true 200m dive rating; Sapphire opens a window on the movement.

Cyclops Crystal Clean 68%Cyclops 32%

Most keep the crystal clean. A bold minority add the cyclops — the date magnifier, NH35 only.

What's in the box, what you'll add

In the box: the case body with pre-installed sapphire crystal (cyclops or no-cyclops, per your selection), the bezel and ceramic insert pre-fitted and pre-aligned with a Swiss Super-LumiNova® BGW9 Grade A lume pip, and your chosen caseback.

You'll add to complete the watch: an SKX013-spec chapter ring (required — it seats the dial at the correct height), a crown (five SKX-style options), a 28.5mm dial, hands, and an NH movement. New to this? Our complete build guide walks through every step.

Movement & compatibility

Movements. The case fits Type M versions of the NH35, NH36, NH38, NH70, NH71 and NH72. Because the Ultra Thin profile leaves very tight clearance between the hands and the sapphire, Type L movements will not fit — confirm your movement type before ordering. The SKX013 Diver 38 is recommended for experienced modders.

Dials & hands. Takes 28.5mm dials — the standard shared across the entire Lucius Atelier line — and NH-compatible hands. Stock SKX007 dials may seat differently, as the original SKX007 has a 4 o'clock crown position with offset dial feet while this case is designed for 3 o'clock dial feet.

Bezel & insert. Dimensionally exclusive to this case. Standard SKX bezels and inserts will not fit, and ours will not fit a stock SKX. They ship pre-fitted; replacement parts come from us.

The dive silhouette that defined an era — finally thinner than the original, and ready to build.