Strap for Master Ultra Thin Moon 36 Stainless Steel / Silver / Alligator

The lug width of the Jaeger-LeCoultre Master Ultra Thin Q1248421 is 17 millimetres. This dimension is proportioned to the 36-millimetre case diameter and is a defining characteristic of this model. To verify the correct measurement, position a digital calliper vertically across the inner pins of both lugs: the resulting distance must be exactly 17 mm. Any measurement error will compromise the strap fit and visual balance on the wrist.

For this model, straps in alligator leather with vegetable tanning are recommended, offering a noble patina and discreet grained texture, or satinised calf leather which visually dialogues with the stainless steel case finishing. A structured rubber or NATO strap represents a versatile alternative for daily wear whilst maintaining the timepiece's aesthetic integrity. Your choice depends on intended use and personal preference regarding colour evolution over time.

Strap replacement requires specific tools: a spring bar tool and possibly a small screwdriver. Position the timepiece on a soft, stable surface, then gently push the spring pin towards the centre to release one lug from the strap. Repeat on the other side. Insert the new strap by aligning the lateral holes with the spring pins and pressing until fully engaged. If you lack experience, consult a qualified watchmaker to avoid damage to the lugs.

Yes, the aftermarket offers bespoke straps specifically designed for the 17-millimetre lug width. Straps produced by specialised manufacturers such as Casati Milano guarantee noble materials, bespoke craftsmanship, and customisation availability. Before purchasing, always verify that the lug width is exactly 17 mm and that documentation confirms compatibility. A quality aftermarket strap can extend the timepiece's versatility without compromising its value or constructive integrity.

A quality leather strap, crafted with vegetable tanning and noble leather, maintains optimal performance for 3–5 years of regular use (approximately 5–6 days weekly). Lifespan varies depending on exposure to moisture, perspiration, direct sunlight, and frequency of wear. A strap protected from extreme environmental factors can exceed 7 years. Patina development and possible fibre thinning are natural processes and do not constitute defect; however, deep fissuring or structural failure of the lug attachment indicates replacement is necessary for safety reasons.