Side by side

Serica Ref. 5303 Diving ChronometervsFormex Reef GMT

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

Ref. 5303 Diving Chronometer
SericaRef. 5303 Diving Chronometer
MSRP $1,768
Reef GMT
FormexReef GMT
MSRP $2,235

At a glance

11 of 29 specs differ
Diameter
Ref. 5303 Diving Chronometer39mm
Reef GMT42mm
Power Reserve
Ref. 5303 Diving Chronometer42h
Reef GMT56h
Water Resistance
Ref. 5303 Diving Chronometer300m
Reef GMT300m
MSRP
Ref. 5303 Diving Chronometer$1,768
Reef GMT$2,235

Full specifications

Case

5 specs
Category
Diver
GMT
Diameter
39mm
42mm
Thickness
12.2mm
11.4mm
Lug-to-Lug
46.5mm
47mm
Lug Width
20mm
22mm

Crystal & Dial

2 specs
AR Coating
Yes
Inner
Dial Color
Enamel Black
Black

Movement

3 specs
Caliber
M100 COSC
Sellita SW330-2
Power Reserve
42h
56h
Complications
COSC
None

Pricing

1 specs
MSRP
$1,768
$2,235

Follow this matchup

Get a note when Serica Ref. 5303 Diving Chronometer vs Formex Reef GMT gets more votes, a community discussion, or a price drop. No account needed.

What people say

Owners + reviewers, side by side

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

Serica Ref. 5303 Diving Chronometer

Owners widely praise the Serica Ref. 5303 Diving Chronometer for its excellent wearability, definitive style, and smooth, confident bezel action. The dual scale on the bezel is noted as surprisingly useful, and the crown action, winding, and hacking are reported to work perfectly. One owner describes the Serica 5303-3 as gorgeous and unique, though another notes the crown can appear comically large. On balance, owners rate the Serica Ref. 5303 Diving Chronometer highly for its blend of unique design and robust functionality.

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.

Keep exploring

More watches worth a look

Matched to the watches above on size, movement, style and price — microbrands first. Open any one to dig in.

Adjacent matchups

People also compared

Comparisons nearby in the catalog — alternatives to the watches above paired against the matchup.