Side by side

Formex Reef 39.5 mmvsLongines ULTRA‑CHRON CARBON

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
ULTRA‑CHRON CARBON
LonginesULTRA‑CHRON CARBON
MSRP $5,550

At a glance

18 of 29 specs differ
Diameter
Reef 39.5 mm39.5mm
ULTRA‑CHRON CARBON43mm
Power Reserve
Reef 39.5 mm56h
ULTRA‑CHRON CARBON52h
Water Resistance
Reef 39.5 mm300m
ULTRA‑CHRON CARBON300m
MSRP
Reef 39.5 mm$2,230
ULTRA‑CHRON CARBON$5,550

Full specifications

Case

6 specs
Diameter
39.5mm
43mm
Thickness
11mm
14mm
Lug-to-Lug
45.5mm
48.9mm
Material
Stainless Steel
Titanium
Finish
Brushed and polished
Caseback
Solid
Screw-down case back

Crystal & Dial

4 specs
Crystal Shape
Flat
AR Coating
Inner
Both sides
Dial Color
Bahama Blue
Silver
Indices
Applied
Applied indexes

Movement

7 specs
Caliber
Sellita SW300-1
L836.6
Beat Rate
28,800 vph
36,000 vph
Power Reserve
56h
52h
Jewels
25
0
Hacking
Yes
No
Hand-winding
Yes
No
Complications
None
Hours, minutes, seconds

Pricing

1 specs
MSRP
$2,230
$5,550

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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.

Longines ULTRA‑CHRON CARBON

The Longines ULTRA‑CHRON CARBON is praised for its lightweight composite case and unique "Batman" aesthetic, with its 5Hz movement widely noted for exceptional accuracy. Owners widely report the high-beat movement is the cheapest 5Hz option available. Some owners find the non-rotating bezel a relief, while others consider it a deal-breaker, noting the watch is no longer a dive watch. On balance, owners and reviewers highly rate the Longines ULTRA‑CHRON CARBON for its cool, lightweight design and the exceptional accuracy of its 5Hz movement.

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