Side by side

Formex Reef GMTvsSeiko Prospex Sea

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

Reef GMT
FormexReef GMT
MSRP $2,235
Prospex Sea
SeikoProspex Sea
MSRP $1,500

At a glance

12 of 29 specs differ
Diameter
Reef GMT42mm
Prospex Sea43.5mm
Power Reserve
Reef GMT56h
Prospex Sea70h
Water Resistance
Reef GMT300m
Prospex Sea200m
MSRP
Reef GMT$2,235
Prospex Sea$1,500

Full specifications

Case

6 specs
Category
GMT
Diver
Diameter
42mm
43.5mm
Thickness
11.4mm
13.3mm
Lug-to-Lug
47mm
51mm
Material
Stainless Steel
Titanium
Water Resistance
300m
200m

Crystal & Dial

2 specs
AR Coating
Inner
Anti-reflective coating on inner surface
Lume
Super-LumiNova
LumiBrite on hands and index(es)

Movement

3 specs
Caliber
Sellita SW330-2
6R35
Power Reserve
56h
70h
Jewels
25
24

Pricing

1 specs
MSRP
$2,235
$1,500

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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 GMT

The Formex Reef GMT is widely praised for its unique porthole case shape, COSC-certified Sellita SW330-2 movement with good finishing, and comfortable quick-release bracelet with on-the-fly micro-adjustment. Reviewers note its robust construction, impressive specifications, and strong value proposition, with a slim 11.4mm profile accommodating 300m water resistance and an exhibition caseback. However, owners widely report the 53mm lug-to-lug span with male endlinks makes it too large for smaller wrists. Some find the bezel action stiff and potentially slippery, and a reviewer desired sharper finishing and edges, deeming the aesthetic too modernist. The GMT variant sacrifices a timing bezel unless swapped, and one owner notes sharp edges on the crown and crown guard. Overall, owners and reviewers highly rate the Formex Reef GMT for its exceptional value and well-executed features, particularly its bracelet system and COSC-certified movement.

From video reviewers

The watch features a COSC-certified SW330-2 GMT movement, which is visible through a sapphire crystal display case back and beautifully decorated. The watch's water-resistance of up to 300m/1000ft is a notable feature. The 42mm diameter may be too large for smaller wrists.

Seiko Prospex Sea

Seiko Prospex Sea owners and reviewers praise its Marinemaster-style aesthetic, excellent case finishing, and impressive LumiBrite lume. The watch is powered by the 6R15 movement with a 50-hour power reserve and comes with both a steel bracelet and a silicone strap. Some owners find the Seiko Prospex Sea to be a great value and a suitable first "proper" watch, while others report it is uncomfortably big, thick, and heavy on smaller wrists. Reviewers note the GMT function is secondary with a less prominent scale, and the bezel's quieter clicks may not appeal to all. On balance, owners and reviewers rate the Seiko Prospex Sea highly for its classic design and finishing at its price point.

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