Black Bay GMT

Ref. M79830RB · “Pepsi”

Case diameter: 41 mm; Manufacturer spec
Lug-to-lug: 50 mm; Measured in a published review
Thickness: 14.6 mm; Measured in a published review
Lug width: 22 mm; Measured in a published review

Retail price $5,275 (US, Oct 2026)

Your wristIdeal fit

Wrist flat: 55.1 mmLug-to-lug: 50 mm

How the Black Bay GMT wears

Its lugs reach 9 mm past the 41 mm case, more than the 7.1 mm typical across the almanac, so it wears larger than its diameter suggests.

On our fit model it sits best on wrists from 7" to 8.25" (17.8–21.0 cm); below 7" the lugs start to reach the edge of the wrist.

At 14.6 mm thick it is thicker than 100% of the 24 other gmt watches we've measured, so expect it to sit tall on the wrist.

Its 22 mm lug width is one of the most common strap sizes; 27 other watches here share it, so aftermarket straps are easy to find.

Will the Black Bay GMT fit your wrist?

With a 50 mm lug-to-lug, here is how it wears across common wrist sizes. We estimate the flat top of each wrist from its circumference; measure yours for a closer answer in the fit finder.

Wrist	Flat width (est.)	Fit
6"	47.2 mm	Lugs overhang
6.5"	51.2 mm	Snug, lugs near the edge
7"	55.1 mm	Ideal fit
7.5"	59.1 mm	Ideal fit
8"	63 mm	Ideal fit

Specifications

Reference: M79830RB
Collection: Black Bay GMT
Status: In production
Introduced: 2018
Case material: stainless steel
Crystal: sapphire
Water resistance: 200 m
Bezel: bidirectional 24-hour, burgundy and blue anodised aluminium insert
Dial: black
Strap / bracelet: riveted steel bracelet, folding clasp with safety catch
Style: GMT, Dive

Movement

Caliber: Tudor MT5652
Type: automatic
Power reserve: 70 hours
Frequency: 28,800 vph (4 Hz)
Jewels: 28
Accuracy: COSC

Compare

Black Bay GMT vs Rolex GMT-Master II

Takes 22 mm straps. See other 22 mm watches and straps.

Watches that wear the same size

Other watches within 1.5 mm of its lug-to-lug.

Same 22 mm lug width

All 22 mm watches

These take the same straps as the Black Bay GMT.