Promaster Mechanical Diver

Ref. NB6021-17E · “Fujitsubo”

Case diameter: 41 mm; Manufacturer spec
Lug-to-lug: —; Not published
Thickness: 12.3 mm; Manufacturer spec
Lug width: 20 mm; Manufacturer spec

Retail price $875 (US, Oct 2026)

We have not verified this watch’s lug-to-lug yet, so we can’t draw it on a wrist. Case diameter alone is a poor guide to fit.

How the Promaster Mechanical Diver wears

At 12.3 mm thick it is slimmer than 75% of the 79 other dive watches we've measured, so it slides under a cuff more easily than most.

Its 20 mm lug width is one of the most common strap sizes; 104 other watches here share it, so aftermarket straps are easy to find.

Specifications

Reference: NB6021-17E
Collection: Promaster
Status: In production
Case material: Super Titanium (Duratect titanium carbide)
Crystal: sapphire
Water resistance: 200 m
Bezel: unidirectional rotating diver's bezel
Dial: black
Strap / bracelet: black polyurethane strap, buckle
Weight: 75 g
Style: Dive

Movement

Caliber: Citizen 9051
Type: automatic
Power reserve: 42 hours
Frequency: 28,800 vph (4 Hz)
Jewels: 24
Accuracy: -10/+20 s/day (static average)

Takes 20 mm straps. See other 20 mm watches and straps.

More Promaster references

Same 20 mm lug width

All 20 mm watches

These take the same straps as the Promaster Mechanical Diver.

Sources