Longines · HydroConquest

Strap for Longines HydroConquest L3.649.4.56.6

The Hydroconquest Automatic 41 takes 21 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

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Lug width21 mm
Case diameter41 mm
ReferenceL3.649.4.56.6 (aka: L36494566)
FamilyHydroConquest
MovementLongines caliber L633.5 Hours, Minutes, Seconds | Date
CaseStainless Steel

Spring bar

Swiss Standard universal spring bars

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

What I'm asked about the Longines HydroConquest L3.649.4.56.6

What strap size does the Longines HydroConquest L3.649.4.56.6 take?

The Longines HydroConquest L3.649.4.56.6 needs 21 mm between the lugs, usually 18 mm at the buckle. It's the size I've been fitting on it for years.

Can the strap on the Longines HydroConquest L3.649.4.56.6 be changed?

Yes. It has spring bars between the lugs: with the right tool the strap comes off in a minute. If you'd rather not risk a scratch, I do it in the workshop.

Can I put a leather strap on the Longines HydroConquest L3.649.4.56.6?

Yes, in 21 mm leather, as long as you don't wear it in the water: leather doesn't like the sea or the pool. For days in the water, rubber. On a 41 mm diver I go for a full-thickness strap, not a thin one. I don't keep rubber ready in 21 mm: write to me and I'll make it.

Which strap do you recommend for the Longines HydroConquest L3.649.4.56.6?

Rubber if you wear it in the water; otherwise a 21 mm calf strap, full thickness. You'll find it ready in the 21 mm collection. If you'd rather have something built on your wrist, the Casati atelier.

Straps for the HydroConquest L3.649.4.56.6

Selected for the 21 mm lug width · workshop selection

All 21 mm straps →

The HydroConquest L3.649.4.56.6, seen from the bench

The Longines HydroConquest L3.649.4.56.6 is a 41mm stainless steel diving watch continuing the heritage of the collection founded in 1959. It features the Longines L633.5 caliber, a manual-wind mechanical movement with hours, minutes, seconds and date window. The unidirectional bezel with 60-minute graduation and 316L steel case ensure reliability for recreational diving. The 21mm lug width accommodates versatile strap options while maintaining elegant proportions on medium to large wrists.

Frequently asked questions

What is the best strap for the Longines HydroConquest L3.649.4.56.6?

The optimal strap depends on your primary use case. For formal elegance, we recommend alligator or vegetable-tanned calf leather, which develops natural patina over time. For diving and sporty applications, an FKM rubber strap or high-density nylon NATO ensures waterproofness and durability. For maximum versatility, a dark brown or black calf strap pairs seamlessly with any occasion. At Casati Milano, you can personalise your choice with expert consultation and bespoke craftsmanship.

Can I use an aftermarket strap on the Longines HydroConquest L3.649.4.56.6?

Yes, the Longines HydroConquest L3.649.4.56.6 is fully compatible with aftermarket straps featuring a 21mm lug width. Bespoke artisanal straps, such as those crafted by Casati Milano, are available in premium leathers (alligator, calf, shell cordovan) or technical materials (FKM rubber, NATO nylon) with construction quality exceeding mass-market alternatives. The only requirement is accurate lug width measurement and confirmation that the strap is designed for 41mm cases.

How long does a leather strap last on the Longines HydroConquest L3.649.4.56.6?

A high-quality artisanal leather strap typically lasts 2–4 years with daily wear, provided it receives appropriate maintenance. Leather should be dried promptly after water exposure and conditioned with specialist balm every 3–4 months. Straps crafted from vegetable-tanned leather develop rich patina and may last beyond 5 years. If the strap experiences frequent immersion, durability reduces to 12–18 months; in such cases, opt for FKM rubber, which offers 3–5 years of wear without degradation. Casati Milano guarantees all bespoke straps for 18 months.

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.

Request an appointment →

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

The atelier's website: casatimilano.com