Seiko SPB317 vs SRPE93
Two Prospex divers that are often weighed against each other: a smaller, better-equipped 6R35 model and the classic 45 mm 4R36 diver at a lower price.
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The short answer
Pick the SPB317 for a smaller, better-specified watch: it is 41 mm across and 12.3 mm thick against the SRPE93's 45 mm and 13.4 mm, with a sapphire crystal and a 70 h 6R35 movement. Pick the SRPE93 to save money: it lists at $525 (US list) vs $900 (US list), with a Hardlex crystal and the 4R36 (41 h).
Both are 200 m ISO 6425 divers per Seiko. Seiko publishes the SPB317's lug-to-lug (46.9 mm) but not the SRPE93's.
Side-by-side specs
| Spec | Seiko SPB317 | Seiko SRPE93 |
|---|---|---|
| Case diameter | 41 mm | 45 mm |
| Thickness | 12.3 mm | 13.4 mm |
| Lug-to-lug | 46.9 mm | Not published by Seiko |
| Lug width | 20 mm | 22 mm |
| Calibre | 6R35 | 4R36 |
| Movement | Automatic | Automatic |
| Power reserve | 70 h | 41 h |
| Hacking seconds | Yes | Yes |
| Water resistance | 200 m | 200 m |
| ISO 6425 diver | Yes | Yes |
| Crystal | Sapphire | Hardlex (mineral) |
| Case material | Stainless steel | Stainless steel |
| Ships on | Silicone | Silicone |
| Weight | 100 g | 124 g |
| US list price | $900 (US list) | $525 (US list) |
| Status | In production | In production |
| Suits wrists of about our sizing guide | 16.4–18.3 cm | 18.1–20.0 cm |
Specs summarised in our own words from the brand's product pages: SPB317 source (checked 23 Oct 2026) SRPE93 source (checked 29 Oct 2026). "Not published" means the brand page we checked doesn't list it, so we leave it blank rather than guess.
Wrist fit
Lug-to-lug (tip of the top lugs to tip of the bottom lugs) decides whether a watch overhangs your wrist more than the diameter does. Enter your wrist to see how each one should wear.
- Seiko SPB317 –
- Seiko SRPE93 –
Same rule of thumb as Watch Finder: case diameter of about 23.5% of your wrist circumference (−2 mm to +2.5 mm), and lug-to-lug no longer than about 29% of it plus 1 mm. A guide, not a rule; flat or round wrists differ.
Strap and lug-width fit
- Seiko SPB317: 20 mm lugs, ships on silicone
- Seiko SRPE93: 22 mm lugs, ships on silicone
The lug widths differ, so a strap bought for one will not fit the other. Seiko does not publish spring-bar diameter or a strap code, so check the hole size on any aftermarket strap. More in our Seiko Turtle strap guide and the Seiko lug width chart.
Which should you buy?
Our sizing guide puts the SPB317 at 16.4–18.3 cm and the 45 mm SRPE93 at 18.1–20.0 cm.
$525 (US list) list buys a 200 m ISO-rated automatic diver with a day-date.
Sapphire is harder than Hardlex mineral glass, so it resists everyday scratches better.
The SPB317 takes 20 mm straps and the SRPE93 22 mm. Both are common sizes; just don't buy one strap for both.
Prices and where to buy
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Questions
Which is bigger, SPB317 or SRPE93?
The SRPE93: 45 mm wide and 13.4 mm thick, vs 41 mm and 12.3 mm for the SPB317.
What is the SRPE93 lug-to-lug?
Seiko does not publish it on the SRPE93 product page, so we leave it blank rather than guess. Measure tip to tip with calipers if you have one in hand.
What lug width do they take?
The SPB317 takes 20 mm straps and the SRPE93 takes 22 mm, per Seiko.
Is the SPB317 worth the extra money?
It costs $900 vs $525 list. The extra pays for a sapphire crystal, a longer power reserve (70 h vs 41 h) and a smaller, thinner case. If none of those matter to you, the SRPE93 is the better value.
Watch.co is independent and not affiliated with any brand. We haven't handled these watches for this page: everything here comes from brand-published specs and our own analysis. Brand names are used only to identify products.