Strap for Spirit Chronograph Flyback 39.5 Stainless Steel / Black / Bracelet

The Longines Spirit L3.721.4.53.6 is fitted with a 20 mm lug width. This measurement refers to the internal distance between the two lugs on the case. It is important not to confuse lug width with the external case diameter: always measure the space between the inner sides of the lugs to verify compatibility with a new strap.

Given the watch's aviator heritage, we recommend straps in alligator or vegetable-tanned calf leather in shades of dark brown, cognac, or burgundy. For versatility, a NATO strap in Cordura canvas in blue or grey maintains the technical aesthetic. For summer wear, a black or navy FKM rubber strap offers comfort and durability.

Remove the watch from your wrist and place the case on a soft cloth. Using a spring bar tool, gently push the internal spring pin towards the opposite side to release the bar. Repeat on both lugs. Insert the new strap by aligning the holes with the pins, then press until the bar clicks into place.

Yes, any strap with a 20 mm lug width is compatible. Milanostraps offers a collection of 20 mm straps in leather, rubber, and textile materials. For a fully bespoke experience, the Casati Milano atelier creates custom straps with your choice of leather, stitching thread colour, and personalised engravings.

A high-quality leather strap with vegetable tanning typically lasts 3-5 years with daily wear, developing a patina that enhances its aesthetic appeal. Longevity depends on exposure to moisture, sweat, and flexing cycles. Casati Milano straps include an 18-month warranty and can be restored at the atelier to extend their lifespan.