Strap for Constellation Manhattan 29 Co-Axial Master Chronometer Sedna Gold / Diamond / Green Aventurine

The lug width of the Constellation 29mm Sedna Gold 131.58.29.20.99.004 measures exactly 18mm. This dimension is the internal distance between the two spring bar pins of the case. Always verify with a caliper that your compatible strap is marked "18mm" and not "17.5mm" or "18.5mm", as even half a millimeter of tolerance can generate friction on the pins.

For the Constellation Sedna Gold we recommend three main choices: (1) Louisiana alligator with veined grain, which generates brilliance in dialogue with rose gold; (2) Vegetable-tanned calf leather Hermès-style, which develops a cognac patina over time amplifying the case value; (3) Shell cordovan from the horse's thigh, the densest and most ductile material for those who accept the initial break-in. All these materials are available in 18mm at MilanoStraps.

Strap replacement requires the removal of the two spring bars that connect the case to the previous strap. Use a spring bar tool (a small steel lever) to press one of the pins downward, creating sufficient space to remove the strap. Insert the new strap into the lug and release the spring: the pin will return to its natural position. Repeat for the other side. The operation takes 2-3 minutes and requires no watchmaking skills if performed with care.

Yes, the Constellation 131.58.29.20.99.004 is fully compatible with aftermarket straps of 18mm lug width. You can fit alligator, calf, shell cordovan, NATO or rubber: the important thing is to verify that the width is exactly 18mm and that the spring bars are in stainless steel (or gold for upgrading). Consult the MilanoStraps catalog for choice of certified materials and colorations.

Durability depends on frequency of use and protection from the elements. An alligator or calf strap on a Constellation worn daily typically lasts 18-24 months before requiring replacement. Shell cordovan, being denser, can reach 3-4 years. Protecting the strap from excessive sweat, chlorinated water and direct sun exposure extends useful life. MilanoStraps offers certified 18mm replacement straps with rapid replacement, and Casati Milano provides 18-month warranty on every bespoke creation.