Side by side

Formex Reef 39.5 mmvsSeiko Astron GPS Solar 2025 Limited Edition

The numbers, the dial colors, the calibers — laid out so you can stop flipping between tabs.

Reef 39.5 mm
FormexReef 39.5 mm
MSRP $2,230
Astron GPS Solar 2025 Limited Edition
SeikoAstron GPS Solar 2025 Limited Edition
MSRP $2,600

At a glance

15 of 29 specs differ
Diameter
Reef 39.5 mm39.5mm
Astron GPS Solar 2025 Limited Edition42mm
Power Reserve
Reef 39.5 mm56h
Astron GPS Solar 2025 Limited Edition40h
Water Resistance
Reef 39.5 mm300m
Astron GPS Solar 2025 Limited Edition100m
MSRP
Reef 39.5 mm$2,230
Astron GPS Solar 2025 Limited Edition$2,600

Full specifications

Case

7 specs
Category
Diver
GMT
Diameter
39.5mm
42mm
Thickness
11mm
12mm
Lug-to-Lug
45.5mm
47.9mm
Lug Width
22mm
14mm
Material
Stainless Steel
Titanium
Water Resistance
300m
100m

Crystal & Dial

3 specs
AR Coating
Inner
Super-clear coating
Dial Color
Bahama Blue
Black
Lume
Super-LumiNova
LumiBrite on hands and index(es)

Movement

4 specs
Caliber
Sellita SW300-1
3X62
Type
Automatic
Quartz
Power Reserve
56h
40h
Jewels
25
10

Pricing

1 specs
MSRP
$2,230
$2,600

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What people say

Owners + reviewers, side by side

Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.

Formex Reef 39.5 mm

The Formex Reef 39.5 mm is widely praised for its refined finishing, comfortable and well-proportioned case design, and impressive specifications for its price point, including COSC-certified Sellita SW300-1 movement and 300m water resistance. Owners and reviewers highlight the tool-less micro-adjust clasp and quick-release spring bars as practical features. Some reviewers note that the 22mm lug width feels slightly disproportionate to the smaller case, and the bracelet could benefit from more taper, though this is a point of contention for some owners who value the overall package. A prototype crown protrusion issue is noted as being addressed for production. On balance, owners and reviewers rate the Formex Reef 39.5 mm highly for its excellent value and well-executed design.

Seiko Astron GPS Solar 2025 Limited Edition

The Seiko Astron GPS Solar 2025 Limited Edition is widely praised for its advanced GPS time and date adjustment capabilities, powered by light to eliminate battery changes. Owners and reviewers highlight its impressive accuracy and the convenience of automatic time zone updates, with some specifically commending the wearability of the 39mm size and its clean, simple design. However, reception of the GPS signal requires an unobstructed view of the sky, and manual time zone adjustments are necessary for Daylight Saving Time on some variants. One owner notes a slight imperfection in chapter ring alignment on the 39mm model. On balance, owners and reviewers rate the Seiko Astron GPS Solar 2025 Limited Edition highly for its satellite-powered timekeeping and improved wearability in the 39mm configuration.

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