Seiko SRPK91
Ref. SRPK91 · In production
- Case37.4 mm
- Thick12.5 mm
- Lug-to-lug44.7 mm
- Water res.100 m
- MovementAutomatic
- CrystalHardlex (mineral)
Seiko SRPK91 size, specs and price at a glance
The Seiko SRPK91 is 37.4 mm wide and 12.5 mm thick, with a lug-to-lug length of 44.7 mm. It takes 18 mm straps and ships on a bracelet. Inside is the 4R36 automatic calibre, water resistant to 100 m. US list price: $415 when we last checked seikowatches.com (29 Oct 2026).
Strap shopping? See our lug width chart.
Overview
The Seiko SRPK91 is a sports watch from the Seiko 5 Sports collection, part of the SNXS series family. It has a 37.4 mm stainless steel case, 12.5 mm thick, 44.7 mm from lug to lug. Inside is an automatic movement (calibre 4R36) with 41 h of power reserve. You also get 100 m water resistance, a hardlex (mineral) crystal and a bracelet.
Who it suits
- Wrists of roughly 15.1–16.8 cm (5.9–6.6 in), by our Watch Finder sizing guide
- Everyday wear including swimming
- People who enjoy seeing a mechanical movement at work
Strengths
- Compact 44.7 mm lug-to-lug suits smaller wrists
- Display caseback shows the movement
- Hacks and hand-winds, so it is easy to set
Trade-offs
- Hardlex (mineral) crystal scratches more easily than sapphire
- 41 h power reserve: it stops after about a day and a half off the wrist
Written by Watch.co from the published specs below. These are not owner reviews.
Full specifications
Case
| Case diameter | 37.4 mm | seikowatches.com · 29 Oct 2026 |
|---|---|---|
| Thickness | 12.5 mm | seikowatches.com · 29 Oct 2026 |
| Lug-to-lug | 44.7 mm | seikowatches.com · 29 Oct 2026 |
| Case material | Stainless steel | seikowatches.com · 29 Oct 2026 |
| Crystal | Hardlex (mineral) | seikowatches.com · 29 Oct 2026 |
| Caseback | Display (see-through) | seikowatches.com · 29 Oct 2026 |
| Water resistance | 100 m | seikowatches.com · 29 Oct 2026 |
| Magnetic resistance | 4,800 A/m | seikowatches.com · 29 Oct 2026 |
| Weight | 125 g | seikowatches.com · 29 Oct 2026 |
Dial
| Luminous material | LumiBrite | seikowatches.com · 29 Oct 2026 |
|---|---|---|
| Date | Day/Date | our classification |
Movement
| Movement type | Automatic | seikowatches.com · 29 Oct 2026 |
|---|---|---|
| Calibre | 4R36 | seikowatches.com · 29 Oct 2026 |
| Made in-house | Yes | seikowatches.com · 29 Oct 2026 |
| Power reserve | 41 h | seikowatches.com · 29 Oct 2026 |
| Hacking seconds | Yes | seikowatches.com · 29 Oct 2026 |
| Hand-winding | Yes | seikowatches.com · 29 Oct 2026 |
Strap / Bracelet
| Bracelet / strap | Bracelet | seikowatches.com · 29 Oct 2026 |
|---|---|---|
| Lug width | 18 mm | seikowatches.com · 29 Oct 2026 |
Other
| US list price (MSRP) | $415 | seikowatches.com · 29 Oct 2026 |
|---|---|---|
| Production status | In production | seikowatches.com · 29 Oct 2026 |
| Style (our classification) | Sports | our classification |
Specs are summarised in our own words from the brand's product page. Each row links its source and the date we checked it. Fields we haven't verified are left out rather than guessed.
Variants with the same specs
Same case, movement and bracelet or strap; typically a different dial or finish.
More in SNXS series
Similar alternatives
Picked with Watch Finder's style tags and sizing.
Comparisons and strap sizing
Questions about the Seiko SRPK91
How big is the Seiko SRPK91?
The case is 37.4 mm wide, 12.5 mm thick and 44.7 mm from lug to lug.
What movement does the Seiko SRPK91 use?
It uses the 4R36 calibre, a automatic movement with 41 h of power reserve.
Can I swim with the Seiko SRPK91?
Yes. It is rated to 100 m.
Does the Seiko SRPK91 have a date?
Yes, it shows the day and date.
How much is the Seiko SRPK91?
The US list price was $415 on seikowatches.com when we checked on 29 Oct 2026. Prices change, so check before you buy.
Will the Seiko SRPK91 fit my wrist?
By our sizing guide it sits best on wrists of about 15.1–16.8 cm (5.9–6.6 in). Use the fit checker on this page to test your own wrist.
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