If you want the larger, classic SKX-style look, start with the Seiko 5 Sports SRPD51. Prefer a smaller case? Consider the SRPK31. For a compact watch whose maker explicitly calls the dial navy, look at the SNXS-series SRPK87. All three share a 4R36 movement and a 10 bar water-resistance rating, but their dimensions and case styles differ. This is a comparison of three documented options, not a complete list of every blue-dial Seiko 5 Sports model sold worldwide.
How the three watches compare
| Model | Dial description in Seiko’s product information | Series | Diameter | Lug-to-lug | Thickness | Lug width | Movement and reserve | Water resistance |
|---|---|---|---|---|---|---|---|---|
| SRPD51 | Blue appearance in product imagery; the page text does not name a dial color | SKX | 42.5 mm | 46.0 mm | 13.4 mm | 22 mm | 4R36 automatic with manual winding; approximately 41 hours | 10 bar |
| SRPK31 | Product imagery; the page text does not specify a shade | SKX | 38.0 mm | 44.2 mm | 12.1 mm | 20 mm | 4R36 automatic with manual winding; approximately 41 hours | 10 bar |
| SRPK87 | “Sporty navy dial” | SNXS | 37.4 mm | 44.7 mm | 12.5 mm | 18 mm | 4R36 automatic with manual winding; approximately 41 hours | 10 bar |
Specifications and descriptions come from Seiko’s official product pages for the SRPD51, SRPK31, and SRPK87. A written color description is available for the SRPK87; the SRPD51 and SRPK31 pages should not be treated as text confirmation of a particular shade.
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Which model suits your priorities?
Choose the SRPD51 for the larger SKX-style presence
At 42.5 mm across and 46.0 mm lug-to-lug, the SRPD51 is the largest of these three by diameter and length. Its 13.4 mm thickness and 22 mm lug width also give it the broadest listed dimensions. Seiko specifies a stainless-steel case, Hardlex crystal, LumiBrite on the hands and indexes, a unidirectional rotating bezel, and a three-fold clasp with secure lock and push-button release. The see-through screw case back is another listed feature.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteThe SRPD51 is the clearest choice here if you want a diver-style bezel and a larger, familiar SKX-series design. Seiko’s US listing gives a regional list price of USD 350; its UK listing gives GBP 290. These are separate market prices, not directly comparable transaction prices or assurances of stock. Check the US listing or UK listing for the market relevant to you.
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Choose the SRPK31 for a smaller SKX-series case
The SRPK31 measures 38.0 mm in diameter, 44.2 mm lug-to-lug, and 12.1 mm thick, with a 20 mm lug width. It is notably narrower and thinner than the SRPD51, though its lug-to-lug length is only 1.8 mm shorter. That distinction matters: diameter alone does not tell you how much space a watch occupies across the wrist.
Its core movement and water-resistance specifications match the SRPD51: a 4R36 with manual winding, day/date display, approximately 41 hours of reserve, and 10 bar water resistance. Seiko’s US page lists it at USD 350, a regional list price rather than a guaranteed sale price. See the official SRPK31 page for the current listing and product imagery.
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Choose the SRPK87 for a compact SNXS-style watch and explicitly navy dial
The SRPK87 is the smallest by diameter at 37.4 mm, but its 44.7 mm lug-to-lug measurement is longer than the SRPK31’s. It is 12.5 mm thick and uses an 18 mm lug width. The case belongs to the SNXS series rather than the SKX series, so it offers a different case style rather than simply being a smaller SRPD51.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteSeiko describes its dial as “sporty navy” and notes an orange seconds hand, which the manufacturer says appeared in many 5 Sports watches in the 1970s. The Norwegian product page lists the same 4R36 movement, approximately 41-hour reserve, day/date, and 10 bar water resistance as the other two watches. The page establishes those details for that listing, not worldwide availability or a price in other markets. See Seiko’s SRPK87 page.
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How to judge fit from the measurements
Use the four listed case dimensions as comparison points, not as a promise of wrist comfort. Diameter describes width across the case; lug-to-lug describes the distance from one end of the lugs to the other; thickness gives the case’s height; and lug width indicates the strap size category. Wrist shape, the way the lugs sit, and personal preference all affect how a watch feels. No hands-on wear testing is available for these comparisons.
- If you are concerned about a watch looking wide, compare diameter: the SRPD51 is 42.5 mm, versus 38.0 mm for the SRPK31 and 37.4 mm for the SRPK87.
- If you are concerned about the watch spanning your wrist, compare lug-to-lug: the SRPK31 is shortest at 44.2 mm; the SRPK87 is 44.7 mm; the SRPD51 is 46.0 mm.
- If case height is a priority, the SRPK31 is thinnest at 12.1 mm, followed by the SRPK87 at 12.5 mm and SRPD51 at 13.4 mm.
Shared movement and water-resistance details
All three official product pages list Seiko’s 4R36 automatic movement with manual winding, day/date display, and approximately 41 hours of power reserve. That shared specification does not establish a particular accuracy rate in daily use; no comparative rate testing is provided here.
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Each is listed as water resistant to 10 bar. This is the manufacturer’s stated rating, not proof of professional dive certification. Follow Seiko’s guidance for use and care rather than inferring a specific diving suitability from the number alone.
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Straps, bracelets, and availability
The listed lug widths make 22 mm straps a sensible search category for the SRPD51, 20 mm for the SRPK31, and 18 mm for the SRPK87. Width is only a starting point: it does not confirm that a particular bracelet’s end links, attachment system, or fit will work with a given watch. Check the exact reference and attachment details before buying a replacement bracelet.
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Regional product pages and prices can change, and a listing does not guarantee current stock. Seiko’s 2023–2024 Japan catalog also includes other 5 Sports references, such as the GMT-style SBSC003 with a 4R34 movement and 42.5 mm case diameter, but that historical catalog entry does not establish present availability or current pricing outside that context. The three watches above are selected examples, not an exhaustive global lineup.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
