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Automatic COSC 300M Green 42 mm
Lugs stay on wrists from about 6.25 in (lug-to-lug rule of thumb)
Last checked Oct 26, 2026
View on Formex’s site ↗From Formex
A true Divers’ watch by design, the 42mm stainless steel watch is powered by a self-winding COSC-certified SW300 that comes in Sellita’s highest quality grade, using top of the line components only found in Chronometer-grade movements. This thin high-precision caliber allowed to construct the REEF at just 11.4mm thickness and a perceived height of 9.4mm, making it a great fit for the elegant occasions alike. For any underwater activities, a double gasket construction is designed and tested for 300 m / 1000 ft of water resistance. Being one of the most exposed parts, the unidirectional rotatable bezel is made of an extremely hard and scratch-resistant Zirconium oxide ceramic. The graduations and numbers are engraved by femto-laser pulsations. Each bezel takes 60 minutes of precision engraving to achieve its three-dimensional effect. Machined gear-like indentations on the bezel’s edge allow a diver the ideal grip to safely set and monitor diving time and decompression stops. The 120 click action is responsive and smooth, yet offers firm and precise function of the bezel. Besides that, the bezel can be changed without the use of any tools. The sunray finished dial is manufactured at Formex’s in-house dial manufacture in the Jura mountains. The gradient for the different colors is sprayed by hand. The REEF’s bold rehaut-style hour markers are also hand-applied and triangle shaped, pointing towards the broad hour and minute hands that share the same detailed beveled mirror polish and brushed top surface finishing. Hands and hour markers as well as a capsule on the bezel’s zero marker are deep-filled with Swiss Super-LumiNova® BGW9 that emits a long-lasting blue glow in dark conditions. Being able to read the time with absolute certainty is a matter of survival when diving. Both the solid-link bracelet and the rubber strap feature a buckle with a patented fine-adjustment system as well as a completely re-engineered and patented quick release system that allows to swap straps without the use of any tools.
Specifications
Details and photos come from Formex’s website, last checked Oct 26, 2026. Specs were read automatically and may contain mistakes.
Case
- Diameter
- 42 mm
- Lug-to-lug
- 47 mm
- Thickness
- 11.4 mm
- Thickness incl. crystal
- Not listed
- Lug width
- 22 mm
- Material
- 316L steel
Movement
- Type
- Automatic
- Caliber
- Sellita SW300-1
- Power reserve
- Not listed
- Functions
- Not listed
Crystal and bezel
- Crystal
- Sapphire
- Bezel
- Not listed
Water resistance
- Rated to
- 300 m
Dial and lume
- Dial
- green
- Lume
- Not listed
Strap
- Strap
- Not listed
Every spec Formex lists
- Now
- (Inc. Tax)
- Case
- Stainless steel 316L
- Bezel
- Unidirectional rotating Zirconium Oxide Ceramic bezel (blue, black, green) / Stainless steel for the steel bezel
- Glass
- Sapphire crystal with anti-reflection treatment
- Height
- 11.4mm (perceived 9.4mm)
- Weight
- 90g (case only) MATERIAL Bezel: Unidirectional rotating Zirconium Oxide Ceramic bezel (blue, black, green) / Stainless steel for the steel bezel
- Diameter
- 42mm
- Lug width
- 22mm
- Lug-to-lug
- 47mm
- DIAL-URL https
- //cdn11.bigcommerce.com/s-uok04hg6nb/images/stencil/original/image-manager/green.png
- Water resistance
- 30 bar (300 metres / 1000 feet)
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