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Longines · Admiral

Strap for Admiral Chronograph Black Brown Strap

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

Lug width

21mm
21 mm strapsAll Longines
Lug width21 mm
Case diameter42 mm
ReferenceL3.666.4.56.3 (aka: L36664563)
FamilyAdmiral
MovementLongines caliber L705.2 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

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Straps for the Admiral L3.666.4.56.3 (aka: L36664563)

Selected for the 21 mm lug width · workshop selection

All 21 mm straps →

The Admiral L3.666.4.56.3 (aka: L36664563), seen from the bench

The Longines Admiral L3.666.4.56.3 is a 42mm stainless steel sports chronograph featuring a deep blue dial with baton indices and an integrated date window. Powered by the Longines L705.2 quartz movement, this elegant instrument balances formal and informal aesthetics without compromise. The 21mm lug width is proportionally calibrated to the case diameter and ensures proper strap compatibility—measuring exactly 21mm between the inner points of each lug attachment.

Frequently asked questions

What is the lug width of the Longines Admiral L3.666.4.56.3?

The lug width of the Longines Admiral L3.666.4.56.3 is 21mm. This measurement represents the distance between the inner points of both lugs. It is essential to verify this before purchasing an aftermarket strap: a 20mm or 22mm strap will not fit correctly into the lugs, compromising both security and aesthetics.

What is the best strap for the Longines Admiral L3.666.4.56.3?

There is no single 'best' strap, but rather choices coherent with the watch's sport-elegant character. Navy alligator offers maximum formality; vegetable-tanned calf in cognac creates dialogue between the blue dial and earthy warmth; burgundy shell cordovan delivers rare elegance and noble ageing. FKM vulcanised rubber remains ideal for those seeking daily practicality without sacrificing sobriety.

How do I change the strap on the Longines Admiral L3.666.4.56.3?

The lugs of the Longines Admiral L3.666.4.56.3 are equipped with a <a href="/pages/termine-glossario/deployante">deployante</a> (folding clasp). To remove the strap: open the <a href="/pages/termine-glossario/deployante">deployante</a> and gently extract the strap from the lugs, one side then the other. To install the new 21mm strap: insert one end into the first lug, then the other end into the second lug, ensuring the strap sits flush against the keeper. Finally, close the <a href="/pages/termine-glossario/deployante">deployante</a>.

Is the Longines Admiral L3.666.4.56.3 strap compatible with other watches?

The 21mm strap is compatible with all watches that have 21mm lugs. However, the design of the Longines Admiral sport watch (blue dial, 42mm stainless steel case) pairs best with aesthetically coherent straps. A bespoke 21mm leather strap designed for the Admiral may not enhance a different watch. For maximum investment value, we recommend straps dedicated to watches of the same formal category.

How long does a leather strap last on the Longines Admiral L3.666.4.56.3?

Longevity depends on leather quality and usage patterns. Quality vegetable-tanned calf, worn daily, lasts 3-5 years before showing significant wear. Alligator resists 5-7 years. Shell cordovan, being rare and robust leather, easily exceeds 7-10 years. Maintenance—monthly cleaning, treatment with specific balms—extends lifespan. Atelier Casati Milano provides 18 months' warranty on bespoke 21mm straps.

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