Seiko Alpinist strap size and lug width
Lug widths for the Alpinist, "Baby Alpinist" and other Prospex Land references, from Seiko's own pages.
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The short answer
Most Alpinists take 20 mm straps, including the SPB121, SPB507 and SPB155. The SPB249 is the exception at 19 mm, so a 20 mm strap won't fit it. Check the table for every Prospex Land reference we track.
Seiko sells these under Prospex "Land". "Alpinist" and "Baby Alpinist" are the names buyers search for.
| SPB155 | Prospex | 20 mm | 38 mm | 46 mm | 12.9 mm | Bracelet | – |
| SPB249 | Prospex · Land | 19 mm | 38 mm | 46.2 mm | 12.9 mm | Bracelet | – |
| SPB289 | Prospex · Land | 19 mm | 38 mm | 46.2 mm | 12.9 mm | Bracelet | – |
| HBC006 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 12.7 mm | Cow leather | – |
| HBC007 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 13.6 mm | Cow leather | – |
| SPB121 | Prospex | 20 mm | 39.5 mm | n/p | 13.2 mm | – | – |
| SPB210 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 13.2 mm | Cow leather | – |
| SPB377 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 13.6 mm | Cow leather | – |
| SPB379 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 13.6 mm | Cow leather | – |
| SPB503 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 12.7 mm | Bracelet | – |
| SPB505 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 12.7 mm | Bracelet | – |
| SPB507 | Prospex · Land | 20 mm | 39.5 mm | 46.4 mm | 12.7 mm | Cow leather | – |
Click a column heading to sort. n/p = not published by the brand. Quick-release "Yes" only where the brand page says so; "–" means not stated, not "no".
Which strap type?
- Rubber or silicone: the practical choice for swimming and hot weather. It doesn't absorb water and rinses clean.
- Fabric single-pass or two-piece nylon: light and cheap. A single-pass strap runs under the case, which adds a little height on the wrist.
- Leather: dressier, but water and sweat shorten its life. Keep it off dive watches you actually swim with.
- Steel bracelet: the most durable, but aftermarket bracelets need end links shaped for the specific case, which brands rarely publish. Buy one listed for your exact reference.
Spring bars: what Seiko doesn't publish
Seiko lists lug width, but not spring-bar diameter or a strap code. Aftermarket straps vary in how large their spring-bar holes are, so before you buy, check the strap's stated hole size against the bars you'll use, or reuse the original bars if they fit. See our spring bars and tools guide.
Shop straps
Paid links to Amazon search results. Check the listed width and spring-bar hole size against the table above.
Questions
What lug width is the Seiko Alpinist?
20 mm for the SPB121, SPB507 and SPB155, per Seiko.
Why is the SPB249 19 mm?
That is what Seiko lists for it. Treat it as its own size when buying straps.
What strap suits an Alpinist?
Leather suits its field-watch look; rubber or a steel bracelet makes more sense if it will get wet often. All are rated to 200 m per Seiko, but leather doesn't like water.
Which Alpinist is the smallest?
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.