Fortis
Cosmonaut 647.28.13— lug 20mm
Fortis Cosmonaut 647.28.13: 20mm strap. Alligator, box calf, shell cordovan and rubber, cut and stitched in Milano. Choose your leather.
Artisanal Note
"This model requires a precise 20mm lug width to preserve the original sartorial balance."
Technical Specifications
Fortis 647.28.13The essential strap measurement.
Browse 20mm straps →647.28.13
ETA caliber 2836-2 Hours, Minutes, Seconds | Date, Day
The Heritage
Compatible Straps
Selected for the 20mm lug width of the Cosmonaut
FAQ
What is the lug width of the Fortis Cosmonaut 647.28.13?
The lug width of the Fortis Cosmonaut 647.28.13 is 20 millimetres. This dimension is the historical standard of pilot watches and cosmonautical chronographs, allowing the strap to pass through even when wearing tactical clothing or spacesuits. To verify the measurement, position a digital calliper between the two spring bar attachments on the case, perpendicular to the bezel.
Which strap pairs best with the Fortis Cosmonaut 647.28.13?
The Fortis Cosmonaut 647.28.13, given its functional and austere nature, pairs ideally with vegetable-tanned leather straps in medium brown coloration, ballistic nylon NATO straps in charcoal grey, or vulcanised rubber straps in black. These materials respect the military aesthetic integrity of the model without excessive formal aspirations. Avoid alligator or shell cordovan straps in vivid colourings, which would create incongruous aesthetic over-qualification.
How do I change the strap on the Fortis Cosmonaut 647.28.13?
The strap replacement procedure requires a lug removal tool or a fine needle and tweezers. Position the watch on a stable surface, identify the spring bars connecting the lugs to the case, and gently press the pin from the inside outward using the tool. The strap will then be released. Insert the new strap by aligning the holes with the lugs, and press the spring bar until it is fully anchored. Verify that the strap is securely positioned before wearing the watch.
Is the Fortis Cosmonaut 647.28.13 compatible with aftermarket 20mm straps?
Yes, the Fortis Cosmonaut 647.28.13 is fully compatible with any aftermarket strap of 20 millimetre width. It is essential to verify that the width measured between the passants is exactly 20 millimetres to guarantee precise fit. Standard-length straps (typically between 90 and 140 millimetres) are generally compatible; for particularly large or small wrists, customised length may be required.
How long does a leather strap last on the Fortis Cosmonaut 647.28.13?
The lifespan of a leather strap depends on usage intensity and material quality. A high-quality vegetable-tanned leather strap, used daily, has an average lifespan of 18–36 months before replacement is required. Exposure to moisture, perspiration, and thermal variations accelerates fibre ageing; periodic maintenance with natural oils (such as mink oil) retards deterioration. Lower-quality chromium-tanned leather straps have a lifespan of 12–18 months. Rubber or NATO straps have significantly longer durability, typically exceeding 48 months.