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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsFormex makes several distinct kinds of watches, but the Reef is the clearest choice if you want a purpose-built diver: both the 39.5 mm and 42 mm models are specified for 300 m water resistance and use a COSC-certified Sellita SW300-1 automatic movement with a stated 56-hour power reserve. The smaller Reef has a shorter 45.5 mm lug-to-lug measurement, versus 47 mm for the 42 mm model. For everyday wear, Formex positions Essence as its flagship collection; the range also includes the carbon-fiber Essence Leggera, Reef GMT and Field Automatic. This is a specification-led review, not a hands-on test, so comfort, accuracy in use, durability and value cannot be independently rated here.
What is Formex, and which collection should you consider?
Formex’s current catalog spans several use cases rather than one universal design. The brand describes Essence as its flagship and bestselling collection, while the Reef line is its dive-watch family. Those are Formex’s own positioning statements, not independent sales rankings.
| Collection | Best fit by intended use | What distinguishes it |
|---|---|---|
| Essence | Everyday wear | Formex describes it as a versatile everyday watch and lists ThirtyNine and FortyOne sizes, among other variants. |
| Essence Leggera | Those interested in lighter, technical materials | Uses carbon fiber and high-tech ceramic, along with Formex’s Case Suspension System. |
| Reef | Diving-oriented styling and water-resistance specification | Available in 39.5 mm and 42 mm sizes; both are specified at 300 m water resistance. |
| Reef GMT | Travel or tracking additional time zones | Adds GMT functionality to the 42 mm platform; Formex describes interchangeable GMT and dive bezels. |
| Field Automatic | Those looking for a field-watch option | A separate current collection in the Formex catalog; the sources cited here do not establish its detailed specifications. |
Formex’s collection catalog is the best place to confirm the live lineup and variants. For the practical operation of its watches, the brand’s video instructions cover tasks such as setting the time and date, changing straps, adjusting bracelets and using fine-adjustment systems.
Formex Reef 39.5 vs. Reef 42: what changes?
The two standard Reef sizes share the headline movement and water-resistance specifications. The clearest documented difference is fit: the 39.5 mm case is narrower and 1.5 mm shorter from lug to lug. That does not guarantee that it will suit every smaller wrist; wrist shape, strap or bracelet choice, and personal preference matter too.
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- Swiss Made Watch
- Movement: Automatic MIDO caliber with Day/Date calendar - Power reserve 80 hours
- Case Type: 41mm Diver-style stainless steel case with silver rotating bezel - Capable of withstanding pressures of up to 20 bar (200 m/660 ft), and equipped with a screw-down crown, this watch offers optimal protection against water. Case Thickness: 11.7mm
- Dial: Blue with grained finish, polished nickelled indexes coated with white Super-LumiNova, day and date at 3 o’clock. Sand-blasted flange with minute indication. Crystal: Sapphire crystal with double sided anti-reflection treatment Crystal: Sapphire crystal with double sided anti-reflection treatmentCrystal: Sapphire crystal with double sided anti-reflection treatment.
- Band Type: Satin-finished stainless steel bracelet with polished central link. Folding clasp with diving extension and engraved MIDO logo. MIDO quick-change system.
| Specification | Reef 39.5 | Reef 42 |
|---|---|---|
| Case diameter | 39.5 mm | 42 mm |
| Case height | 11.0 mm | 11.4 mm; Formex also gives a perceived height of 9.4 mm |
| Lug to lug | 45.5 mm | 47 mm |
| Lug width | 22 mm | 22 mm |
| Water resistance | 300 m / 1000 ft | 300 m / 1000 ft |
| Movement | Sellita SW300-1 automatic, chronometer grade and COSC-certified | Sellita SW300-1 automatic, chronometer grade and COSC-certified |
| Stated power reserve | 56 hours | 56 hours |
Specifications are from Formex’s Reef 39.5 product page and Reef 42 product page. Compare lug-to-lug as well as diameter when checking fit, and try a watch on if possible. Formex describes the Reef 39.5 as the compact option and the 42 as the original Reef size; its product copy calls the 42 the bestselling Reef size.
What the COSC certification and reserve mean
COSC is the Swiss chronometer-certification body. Formex says each Reef movement receives COSC certification through a 15-day rate test, followed by an additional rate test after the watch is assembled. These are the manufacturer’s stated procedures, not independent test results for this review. The 56-hour reserve is also a stated specification: it indicates how long a fully wound watch is intended to run off the wrist before stopping, not a guarantee of real-world running time under every wearing pattern.
Rank #2
- Case size: 40.50 mm: Band Width: 20.00 mm: Case Thickness: 14.10 mm
- Automatic , Powermatic 80, Nivachron, Date
- Band Type: Steel: Band Length: 179.64 mm
- Water-resistant up to 300 m / 990 ft: suitable for diving and/or snorkeling.
- 2 Year International Warranty
What the 300 m rating does—and does not—tell you
Formex specifies both Reef sizes at 300 m / 1000 ft. That is a water-resistance rating, not a promise that every watch will remain watertight indefinitely or that every example has been independently tested for this article. Follow the current manufacturer instructions for use and maintenance, particularly before exposing a watch to water.
Materials, interchangeability and adjustment
Formex describes the Reef 39.5 as having a 316L stainless-steel case, sapphire crystal with anti-reflective treatment, and unidirectional ceramic bezel options made from zirconium oxide. Its product pages describe tool-free interchangeability for straps, bracelets and bezels, as well as a fine-adjustment deployant clasp with up to 7 mm of gradual adjustment on the Reef 39.5. The 42 mm page also describes interchangeable components and fine adjustment.
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Rank #3
- Swiss Made Watch
- Movement: Automatic MIDO caliber with Day/Date calendar - Power reserve 80 hours
- Case Type: Diver-style Titanium case with black rotating bezel - Capable of withstanding pressures of up to 20 bar (200 m/660 ft), and equipped with a screw-down crown, this watch offers optimal protection against water.
- Case Size: 42.5mm - Case Thickness: 11.8mm - Anthracite color dial offering indexes filled with Super-Luminova and skeletonised hands - Crystal: Sapphire crystal with double sided anti-reflection treatment
- Band Type: Titanium bracelet - Folding clasp with diving extension - Band Width: 22mm
These design features may make configuration changes and incremental fit adjustment more convenient, but ease of changing parts and comfort are wearer-dependent. The manufacturer’s instructions page provides videos for strap and bracelet changes and clasp adjustment. Check compatibility for the exact watch and replacement component before ordering; a shared brand name alone does not establish that a part fits every model.
How Reef compares with Essence and Reef GMT
Reef or Essence?
Choose between them by intended role, not just brand or movement language. The Reef is the more explicitly dive-oriented option, with a rotating bezel and a published 300 m rating. Formex frames Essence as a versatile everyday collection and highlights its Case Suspension System and fine-adjustment clasp. The material here does not establish a like-for-like movement, dimensions, price or independent performance comparison across the full Essence range, so check the specific reference you are considering rather than assuming all models share one specification.
Rank #4
- Case Size: 40.00 mm, Band Width: 20, Case Thickness: 9.97 mm
- Quartz movement, 316L stainless steel case, Index dial type, Date
- Stainless steel strap/bracelet, interchangeable quick release bracelet,folding clasp with safety and push-buttons closure
- Water-resistant up to a pressure of 30 bar (300 m / 1000 ft): suitable for short periods of recreational swimming and showering, but no diving or snorkeling.
- 2 Year International Warranty
Reef or Reef GMT?
The Reef GMT is worth considering if tracking another time zone is useful to you. Formex describes it as a 42 mm Reef platform with GMT functionality and interchangeable GMT and dive bezels. That added function is not a universal upgrade: it brings a different bezel and time-zone use case, and the standard Reef 39.5 may be a better starting point if compact dimensions matter more. Consult the live listing for the exact GMT dimensions and configuration.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What changed in the Reef lineup in 2026?
In an article published April 16, 2026, watch publication Fratello covered a forged-carbon Reef 39.5 variant. It reported a carbon dial and bezel insert with a pattern that varies between examples, while describing the familiar 39.5 × 45.5 × 11 mm case, 300 m rating, COSC-certified movement and 56-hour reserve. The article also says the quick-release bezel and interchangeable strap-and-bracelet platform remain. This is specialist coverage, not a controlled or long-term test. See Fratello’s report on the forged-carbon Reef 39.5; check Formex’s live catalog for current availability in your region.
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- BUILT FOR TOUGH, ACTIVE DAYS Handle outdoor routines and daily wear with confidence. 42mm 316L stainless steel case delivers strength and durability, making it a reliable rugged option for men who need performance in real-world conditions.
- RELIABLE TIME YOU CAN TRUST DAILY Stay on track from work to weekend activities. Swiss-made Ronda 515 quartz movement delivers accurate, consistent timekeeping you can depend on throughout your day.
- DESIGNED FOR WATER AND ACTIVE USE Move from daily wear to time in the water with ease. Unidirectional rotating bezel helps track time during swimming and outdoor activities, making it a practical dive watch for active lifestyles.
- READY FOR SWIMMING AND WATER EXPOSURE Built for everyday wear and ready for swimming or time in the water. Water resistance up to 100M (330FT) supports underwater use and active environments without added stress. The best gift for an active man anyday.
- PRACTICAL DESIGN FOR EVERYDAY CONVENIENCE Keep your day organized without distraction. Date display adds quick access to daily information while maintaining a clean, easy-to-read dial for regular use.
Warranty and buying checks
Formex’s Reef product information states a three-year international warranty and describes free return shipping and repair within two weeks for a covered malfunction or movement defect. Those are manufacturer statements, and coverage depends on the applicable warranty terms, geography and the nature of the issue. Read the current terms before relying on a repair timeline or assuming a particular problem is covered.
- Confirm the exact reference, material and bezel configuration: availability can differ by variant and region.
- Compare lug-to-lug against a watch that already fits you, not diameter alone.
- Check that any replacement strap, bracelet, clasp or bezel is specified for your particular Reef reference.
- Review the current warranty terms and seller status before purchase.
- Use Formex’s product listing for live stock and configuration information; availability may change.
The cited specifications and features are manufacturer-published. They do not establish measured accuracy outside the stated certification process, long-term durability, service outcomes, resale value or owner satisfaction.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
