Jaeger-LeCoultre
Master Control 4018420 (aka: Q4018420)— lug 20mm

The Jaeger-LeCoultre Master Control 4018420, also known as Q4018420, has a 20mm lug width. This is the internal distance between the two case lugs where the springbar is inserted. When replacing the strap, you must choose straps with 20mm lugs to ensure precise fit and correct aesthetics.

For the Master Control 4018420, a Mississippiensis alligator strap is the most fitting choice given the timepiece's formal character: the regular grain and patina that develops over time enhance the 899AC manufacture caliber. Box-grain calf is the everyday alternative for those seeking greater wear resistance. For sportier contexts, a nylon NATO or vulcanized rubber strap provide functionality without compromising the watch's character.

To replace the strap on the Master Control 4018420, you need a springbar tool—a double-pronged instrument that allows you to compress the springbars, the spring pins connecting the strap to the case lugs, without scratching the steel. Insert the forked tip between the lug and the strap, compress the springbar inward, and remove the strap end. The operation takes only a few minutes and requires no technical assistance, provided you use the correct tool and proceed carefully on polished surfaces.

Yes, any strap with 20mm lugs is technically compatible with the Master Control 4018420. Milano Straps offers a selection of artisanal 20mm straps in various materials—alligator, calf, NATO, rubber—designed to respect the proportions of the 40mm case. Casati Milano also produces bespoke straps tailored for those desiring customized craftsmanship in leather choice, color, and buckle.

The lifespan of a leather strap depends on the material, care, and daily use. A high-quality alligator strap, with periodic maintenance using products specific to exotic leathers, can last between three and five years of regular use. Box-grain calf, more resistant to moisture, has similar or greater longevity. Prolonged exposure to sweat and water accelerates degradation: in these conditions it is preferable to alternate the leather strap with a rubber or NATO option. Casati Milano straps are covered by an 18-month warranty against manufacturing defects.