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Omega · X-33 / Z-33

Strap for Speedmaster X-33 Titanium / Bracelet / Military

Takes 20 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width

20mm
20 mm strapsAll Omega
Lug width20 mm
Case diameter42 mm
Reference318.90.42.79.01.001
FamilyX-33 / Z-33
MovementOmega caliber 1666 hours, minutes, small seconds, Additional 24 hours Hand (adjustable) | date, month, perpetual calendar, year indicator | Chronograph, countdown, Flyback, Foudroyante, Rattrapante | alarm
Year2006 - 2010
CaseTitanium

Recommended spring bar

Spring bars Omega 20mm — 1.8mm diameter

Technical match for lug width and diameter · lug 20 mm · Ø 1.8 mm

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Straps for the X-33 / Z-33 318.90.42.79.01.001

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The X-33 / Z-33 318.90.42.79.01.001, seen from the bench

The Omega Speedmaster X-33 Titanium (ref. 318.90.42.79.01.001) is a professional chronograph developed with ESA and international aerospace agencies. Built in grade 5 titanium with a quartz caliber 1666 movement featuring thermal compensation, it delivers precision in extreme environments from pressurized cabins to orbital conditions. The 42 mm case houses complications including flyback chronograph, foudroyante, perpetual calendar with year indicator, alarm, countdown, and adjustable 24-hour hand for circadian monitoring. The 20 mm lug width is specific to this model and ensures precise strap compatibility.

Frequently asked questions

What is the exact lug width of the Omega X-33 / Z-33 318.90.42.79.01.001?

The lug width of the Omega X-33 / Z-33 318.90.42.79.01.001 is exactly 20 millimetres. This measurement is critical for strap compatibility: it is not possible to use 19mm or 22mm straps. The measurement must be verified with a digital calliper, measuring the internal space between the case lugs (the lugs themselves) that will anchor the strap.

Which strap material is most suitable for the Omega X-33 / Z-33?

For the 318.90.42.79.01.001 model, we recommend prioritarily black alligator or dark brown alligator, which respects the space-aeronautical heritage. Excellent alternatives are shell cordovan in mahogany colour (for natural lustre and durability) or vegetable-tanned calf leather (for evolutionary patina). For humid or underwater environments, FKM rubber straps (Viton) offer maximum chemical resistance and waterproofing.

How do you change the strap on the Omega X-33 / Z-33 318.90.42.79.01.001?

Strap replacement requires extraction of the case spring bars using a dedicated tool (spring bar tool). Position the tool under the spring bar, push inward to release the internal spring, then extract the spring bar. Insert the new strap by aligning it with the lugs, then reinsert the spring bar and verify that both sides are correctly anchored. If you are not experienced, we recommend contacting a specialist watchmaker to avoid damage to the titanium case.

Is the Omega X-33 / Z-33 318.90.42.79.01.001 compatible with aftermarket straps?

Yes, provided the strap is specifically made for 20mm lug width. Many artisanal aftermarket straps are compatible with this model and offer superior quality to Omega OEM straps. Always verify the dimensions and, if possible, contact the manufacturer to confirm compatibility before purchase. Online you will find a wide selection of 20mm straps ready for shipping.

How long does a leather strap last on the Omega X-33 / Z-33?

Durability depends on the material and usage. Quality alligator offers 3-5 years of daily use before requiring replacement. Shell cordovan, being denser, can last 5-7 years. A vegetable-tanned calf strap, while softer, develops a natural protective patina and can last 4-6 years. FKM rubber remains stable for 5-8 years, with gradual degradation due to UV exposure and temperature. Regular maintenance (gentle cleaning and conditioning) significantly extends longevity.

The next step

The right strap isn't chosen. It is built, together.

From the atelier appointment to delivery, every step is made for those who know that things done well take time. Rare leathers, one piece at a time, eighteen months of warranty.

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Casati Milano · Via XX Settembre 15, Milan · by appointment only