The Formex Reef 39.5mm pairs a compact-diameter stainless-steel case with a COSC-certified Sellita automatic movement, 300m water resistance and a bezel designed to swap by hand. Official specifications establish its dimensions and functions; the impression that it wears more discreetly than the 42mm Reef comes from Fratello reviewer Thomas Van Straaten’s 2023 account, not a universal fit test.
What the Reef 39.5mm offers
The Bahama Blue model is a stainless-steel automatic diver with a date display and a blue ceramic bezel. Formex lists a Sellita SW300-1 movement that is Swiss made, self-winding and COSC-certified as a chronometer. The manufacturer specifies 25 jewels, a custom skeleton rotor and a 56-hour power reserve.
Formex describes a chronometer as “a watch that has been tested and certified to meet the most strict precision and accuracy standards.” That is the manufacturer’s explanation on its Reef product page. COSC certification indicates testing and certification against precision standards; the listed 56-hour reserve is a separate specification, not a claim about how long the watch will run under every pattern of wear.
Case dimensions and water resistance
Formex’s official Bahama Blue specifications give the following measurements:
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match#1 Best Overall
- High Quality 2350 Automatic Movement
- 42mm Luxury Rose Gold Case
- White Dial with Three Counters, Date Day at 3:00
- Calfskin Strap with Deployment Buckle
- Transparent Case Back, Water Resistance 100 Meters
| Specification | Official figure |
|---|---|
| Case diameter | 39.5mm |
| Case height | 11.0mm |
| Lug-to-lug | 45.5mm |
| Lug width | 22mm |
| Case-only weight | 75g |
| Water resistance | 30 bar / 300m / 1,000 feet |
The case is 316L stainless steel, with a sapphire crystal treated with anti-reflective coating. The 39.5mm diameter is only one part of how a watch sits on a wrist: the 45.5mm lug-to-lug span and strap or bracelet configuration also matter. These measurements provide a useful basis for comparison, but they do not determine fit for every wearer.
Is 39.5mm too small, or different from the 42mm Reef?
In his December 7, 2023 hands-on article, Thomas Van Straaten characterized the 39.5mm Reef as more subdued, slender and versatile than the 42mm version. He also reported that both sizes fit most members of the Fratello office team. Those are one reviewer’s observations in a particular group, not a guarantee that either size will suit a particular wrist.
Rank #2
- Stainless steel case 40mm diameter x 14.1mm thick; Exhibition case back; Black dial; Luminous hands.Band Length: 205mm
- NH35A Japanese Automatic movement, 24 jewel; Assembled in Malaysia; Watch weight 155 grams
- Includes gift box, instructions and 3 year limited manufacturer warranty; Invicta Customer Service can be reached at 1-800-327-7682 for questions (re: Additional links, band replacement, band adjustment, warranty questions, etc.)
Use the official 39.5mm dimensions as a starting point, then consider the 42mm model’s larger diameter, your wrist and how much visual presence you prefer. The reviewed material does not provide a complete, directly comparable set of current official measurements for the 42mm Reef, so it cannot establish every dimensional difference between the two.
Bezel, bracelet and strap changes
Formex specifies a 120-click unidirectional bezel. The blue ceramic bezel can be exchanged by hand among four Reef 39.5mm options, and the brand says its straps and bracelets use quick-release fittings that need no tools. That makes it possible to change the watch’s appearance without treating bezel, strap and bracelet swaps as the same operation: the bezel is an interchangeable component, while the strap or bracelet attaches through its quick-release system.
Rank #3
- Stainless steel case 42mm diameter x 14.2mm thick; Exhibition case back; Black dial; Luminous hands and hour markers
- NH35A Japanese Automatic movement, 24 jewel; Assembled in Malaysia; Watch weight: 142 grams
- Stainless steel band, 215mm L x 22mm W; Band is adjustable by adding/removing links; Fold over safety clasp
- Mineral crystal; Screw-down crown; Uni-directional stainless steel bezel with black and green top bezel ring; 200 meter water resistant: Suitable for professional marine activity and surface water sports. Suitable for diving.
The carbon-fiber-composite deployant clasp has up to 7mm of gradual fine adjustment. Formex notes that a separately purchased strap does not include a clasp, so check whether the strap you are considering can use a clasp you already own or requires a separate purchase. Fratello’s 2023 introduction listed three-row steel, Milanese mesh and hobnail-pattern rubber options, all 22mm wide; that is a launch-era selection, not confirmation of current availability.
Availability and buying checks
Formex’s Bahama Blue product page reported the model as completely sold out when accessed on October 4, 2026. This is a dated snapshot of the official page, not a statement about later stock or availability at other sellers. Check the official product page and any seller directly before making a purchase decision.
Rank #4
- OUR STORY: We design and manufacture reliable, robust watches inspired by timeless watchmaking aesthetics of the ‘60s, and ‘70s and '80s. Our watch designs blend the best of historical design references with contemporary updates and improved functionality and performance. modern watchmaking technologies in creating a collection that is a complete wardrobe of style and performance expectation.
- HENRI DIVER AUTOMATIC : Experience the convergence of exquisite design and top-notch performance with the Henri Diver Automatic. Crafted with intricate Japanese automatic movement, this timepiece features a bi-directional turning bezel and a ravishing brass dial with wave pattern. This timeless aesthetic is paired with water resistance of 20 ATM. A true timepiece of precision and sophistication.
- MOVEMENT: The Henri Diver Automatic is powered by a Japanese TMI NH35 24 Jewels 3 hands date self-winding automatic movement
- THE FINER DETAILS: Featuring a 41mm stainless steel case, 20mm solid stainless steel bracelet, anti reflection coated sapphire lens and water resistance of up to 20 ATM.
- WARRANTY: 2 years International Warranty
Fratello’s 2023 article gave a starting price of €1,830 at the model’s launch. That is historical launch pricing, not a current quote. Formex lists a three-year international warranty; confirm the applicable warranty terms with the seller when buying.
- Confirm the exact Reef 39.5mm variant and whether it is available from the seller.
- Check whether the quoted configuration includes a bracelet, strap and clasp, and whether any accessory is sold separately.
- Compare the 39.5mm case dimensions with a watch that already fits you, especially its lug-to-lug span.
- Verify current price, delivery terms and warranty coverage at the point of sale.
What the available evidence does—and does not—show
The published specifications establish the Bahama Blue Reef’s dimensions, movement, certification, water-resistance rating and interchangeable components. Fratello’s 2023 account adds a reviewer’s impressions of the 39.5mm model beside the 42mm Reef. Neither source establishes a universal fit result or controlled performance comparison against other divers. Fratello’s 2026 introduction of a Forged Carbon Reef describes shared family dimensions of 39.5 × 45.5 × 11mm, 300m water resistance and a 56-hour reserve, but its variant-specific launch prices and limited initial run apply to that carbon model, not Bahama Blue.
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Quick Recap
Best Value
- Steel and gold tone stainless steel case 40mm diameter x 14mm thick; Exhibition case back; Black dial; Luminous hands and hour markers
- NH35A Japanese Automatic movement, 24 jewel; Assembled in Malaysia; Watch weight: 152 grams
- Steel and gold tone stainless steel band, 205mm L x 20mm W; Band is adjustable by adding/removing links; Fold over safety clasp
- Mineral crystal; Screw-down crown; Unidirectional stainless steel bezel with black top bezel ring; 200 meter water resistant: Suitable for professional marine activity and surface water sports. Suitable for diving.
- Automatic movement means that this timeless watch powers a quality Japanese-automatic movement with the simple movement of your arm.
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.
