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Doxa · SUB 300

Strap for SUB 300T Divingstar

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 Doxa
Lug width20 mm
Case diameter43 mm
Reference840.10.361.31
FamilySUB 300
MovementETA caliber 2824-2 hours, minutes, seconds | date
Year2019
CaseStainless Steel

Spring bar

Swiss Standard universal spring bars

The right category for this model · 316L steel, all lug widths 13–26 mm

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Straps for the SUB 300 840.10.361.31

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The SUB 300 840.10.361.31, seen from the bench

The Doxa SUB 300 840.10.361.31 is a diving instrument born in 1967 that equipped oceanographic expeditions when the industry struggled with abyssal pressure challenges. The 42.50mm stainless steel case features an orange dial functioning as a beacon in the depths, with a protected crown designed for extreme underwater environments. The ETA caliber 2824-2 movement provides reliable timekeeping with hours, minutes, seconds and date window. The 20mm lug width is a precise construction specification requiring exact dimensioning to ensure secure mounting and coherent visual proportions on the wrist.

Frequently asked questions

What is the lug width of the Doxa SUB 300 840.10.361.31?

The Doxa SUB 300 840.10.361.31 features a precise lug width of 20 millimetres. This dimension is specific to the model and corresponds to the width between the lugs (the metal pins that support the strap). Measured from inside to inside, it ensures that only 20mm straps mount correctly without slack or jamming in the attachments.

Which strap is most recommended for the Doxa SUB 300?

For the Doxa SUB 300, we recommend straps in alligator or vegetable-tanned calf leather if you seek narrative elegance with natural moisture resistance. If you prioritise extreme practicality for aquatic environments, a NATO in woven nylon offers zero maintenance and rapid drying. For aesthetic-functional balance, a rubber strap in black or dark blue maintains technical language without grip compromise. Avoid delicate leathers: the watch is vocationally designed to face marine environments.

How do I change the strap on my Doxa SUB 300 840.10.361.31?

Strap change is a manual operation requiring no specialist tools. Locate the two metal pins connecting the strap to the case lugs. With care, gently lever outward to extract the first pin: it will slide out horizontally. Repeat on the second pin. The strap now separates from the case. Insert the new 20mm strap by aligning the holes with the pins, then reinsert the pins by pushing until locked. Verify the strap is secure before wearing the watch.

Can I fit an aftermarket strap on this model?

Yes, any strap with a 20mm lug width is compatible. However, only straps dimensioned exactly 20mm guarantee secure mounting and visual proportions coherent with the 42.50mm case. Avoid universal undersized straps (18mm) which slip, or oversized (22mm) which do not enter the lugs. All compatible straps on MilanoStraps are verified against this specification.

How long does a leather strap last on a diving watch?

Durability depends on usage intensity and environment. A vegetable-tanned leather strap with moderate humidity exposure can last 3–5 years before replacement. If exposed frequently to salt water or chlorine, lifespan reduces to 18–24 months. For intensive aquatic-only use, we recommend rubber or NATO. Each strap develops natural patina over time: this is character, not deterioration. Regular maintenance (drying after water exposure) significantly extends useful life.

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