Longines · HydroConquest

Strap for Hydroconquest Chronograph Quartz

Takes 21 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width21 mm
Case diameter41 mm
ReferenceL3.690.4.59.6 (aka: L36904596)
FamilyHydroConquest
MovementLongines caliber L541 Hours, Minutes, Small Seconds | Date | Chronograph
CaseStainless Steel

Spring bar

Swiss Standard universal spring bars

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

Straps for the HydroConquest L3.690.4.59.6 (aka: L36904596)

Selected for the 21 mm lug width · workshop selection

All 21 mm straps →

The HydroConquest L3.690.4.59.6 (aka: L36904596), seen from the bench

The Longines HydroConquest (reference L3.690.4.59.6) is a diving chronograph equipped with the L541 caliber. The movement offers hours, minutes, small seconds, date and chronograph functions. The watch features 21mm lugs for the strap.

Frequently asked questions

What is the lug width of the Longines HydroConquest L3.690.4.59.6?

The lug width is 21mm. Measured internally from one lug to the other, perpendicular to the case. This measurement is specific to this generation of HydroConquest and does not represent a universal standard—many entry-level straps stop at 20mm or 22mm.

What is the best strap for the Longines HydroConquest L3.690.4.59.6?

It depends on usage. For elegance and natural patina, we recommend alligator in stone grey or vegetable-tanned calf in dark tobacco. If you dive regularly, vulcanised rubber in black offers superior resistance to moisture and salt spray. NATO in navy trama is ideal for casual contexts.

How do you change the strap on an HydroConquest L3.690.4.59.6?

The integrated case requires precision: remove the original strap by unscrewing the lug pins (spring bars) from both sides. Proceed with extreme caution to avoid scratching the satin-finished case. Insert the new 21mm strap, aligning it perfectly without forcing. If uncertain, consult a specialised artisan.

Does an aftermarket compatible strap work well on this model?

Yes, provided it is 21mm and of artisanal quality. Entry-level aftermarket straps (synthetic polyester, approximate finishes) betray the chronograph's engineering. Investing in structured alligator, vegetable-tanned calf, or premium rubber preserves the instrument's identity.

How long does a leather strap last on a regularly-worn HydroConquest?

It depends on material and wear. Structured alligator resists 4-6 years if subjected to moderate moisture; vegetable-tanned calf 3-5 years; rubber 5-7 years. Each ages visibly, increasing patina. With periodic lubrication and protection from extreme humidity, durability increases significantly.

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