Seiko › GMT › Prospex › SPB381
Seiko SPB381
Prospex · Sea. Sold new
Video reviews
Hodinkee · YouTube
WatchChris · YouTube
Videos are made by independent reviewers and play from YouTube; they’re not ours. We picked ones that name this reference. Own one? Share your photos.
Where to buy
New · grey market (unauthorized)
Often cheaper. Covered by the store’s own warranty, not Seiko’s.
Pre-owned
Check condition, box and papers. Usually no warranty.
Search links show live listings, so check the exact reference before you buy. Prices change; each one shows when we checked it. We may earn a commission from some links. It doesn’t change your price or which stores we list. Authorized vs grey market vs pre-owned.
The basics
Price
$1,500
Seiko US list, 2026-10-23
Size
42 mm × 12.9 mm
48.6 mm lug to lug
Strap width
20 mm
Any 20 mm strap fits
Water resistance
200 m
Sapphire crystal
Yes
Lume
Hands, markers and bezel
Screw-down crown
Yes
Will it fit my wrist?
Rough rule of thumb from lug-to-lug length (48.6 mm), not a promise. Wrist shape matters; try one on if you can.
How it works day to day
Movement
Automatic, hand-winding
Caliber 6R54, rated +25 to -15 seconds per day
Bezel
Unidirectional rotating
Ceramic insert
Hacking seconds
Yes
Seconds hand stops when you pull the crown, so you can set the time exactly
Hand-winding
Yes
Power reserve
About 72 hours