Seiko 5 Sports SRPD55

The fully specified mechanical in our cluster: Seiko publishes diameter, thickness, lug-to-lug and weight, but hosts no owner reviews

Verdict

The Seiko 5 Sports SRPD55 is the mechanical in our everyday cluster with the most complete spec sheet. Seiko's US product page, checked October 16, 2026, lists caliber 4R36 with approximately 41 hours of power reserve, a 42.5 mm diameter, 13.4 mm thickness, 46.0 mm lug-to-lug, 22 mm between the lugs, 10 bar water resistance, Hardlex crystal, a stainless steel case with a see-through screw case back, a three-fold clasp and a weight of 170.0 g, at USD 350.00. Seiko's 4R36 instruction manual adds the accuracy band: plus 45 to minus 35 seconds a day when worn at 5 to 35 degrees C. This is a documentation review built from those Seiko pages and the Seiko USA warranty; we did not wear or test the watch. The sheet's weaknesses are the ones mechanical buyers already know: a 13.4 mm case, 170 g on the bracelet, a Hardlex rather than sapphire crystal, and an allowed drift that is more than a minute a week at the limit. The gap in this review is owner data. Seiko's US store hosts no reviews, and the retailer and forum pages checked on October 16, 2026 could not be read, so this page reports no owner score and says so rather than borrowing one.

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At a glance

What the SRPD55 actually is

The SRPD55 is the black-dial, steel-bracelet reference in the Seiko 5 Sports line that Seiko's own page files under the SKX series. It is the shape Seiko introduced in 2019 to replace the SKX diver, with the same 42.5 mm case but a 10 bar rating and a push-pull crown instead of a diver's specification.

Inside is caliber 4R36: automatic winding with manual winding, stop-seconds, day and date, 24 jewels, 21,600 vibrations per hour and approximately 41 hours of reserve, all from Seiko's page checked October 16, 2026.

This is a documentation review. Wrist & Sole reads the maker's spec sheet, manual and warranty, plus owner reviews on the maker's store when they exist. We do not wear or test watches. For the SRPD55, owner data is the missing piece, and this page explains why below. The rubric is on our method page.

Who the SRPD55 is best for

The sheet describes a mechanical for people who want the mechanics visible and the fit numbers in writing.

• First-automatic buyers who want hacking and hand winding at a mid-three-figure list price
• Owners who change straps: a 22 mm lug and a standard spring-bar fitting
• People who want a rotating bezel and a 100 m rating without buying a full diver
• Buyers who read lug-to-lug before ordering; Seiko prints 46.0 mm
• Anyone who values a three-year maker warranty over Casio's and Timex's one year
• Who should skip it: people who need quartz accuracy, slim cases under 12 mm, or sapphire at this price

Diameter 42.5 mm, lug-to-lug 46.0 mm, thickness 13.4 mm: the full fit sheet

Seiko's US page lists Diameter 42.5mm, Thickness 13.4mm and Lug-to-lug 46.0mm, with Distance between lugs 22, checked October 16, 2026. Seiko's US store page confirms the 22 as millimeters. The page also prints Weight 170.0g.

That is the most complete fit sheet of the four watches in our everyday cluster. Citizen's BN0150 page gives width and lug width only; Timex gives diameter, height, lug width and weight; Casio gives three dimensions and weight but no lug width because its band is integrated.

The numbers are not small. At 13.4 mm the SRPD55 is 1.6 mm thicker than the Casio GA2100 and 0.4 mm thicker than the Timex Marlin's 13 mm. At 170.0 g on the bracelet it is more than three times the Casio's 51 g and three times the Timex's 56.65 g, by our editors' comparison of the makers' published figures.

The 46.0 mm lug-to-lug is short relative to the diameter, which is what makes a 42.5 mm case workable on a range of wrists. We state the figure; whether it suits a given wrist is a measurement the buyer makes, not something we infer.

Water resistance: 10 bar, a bezel, and what the manual allows

Seiko rates the SRPD55 at 10 bar on the product page. The watch carries a unidirectional rotating bezel and LumiBrite on the hands and indexes, both listed on the sheet, and a see-through screw case back.

Seiko's instruction manual for the 4R calibers, read October 16, 2026, sets out what the markings mean. WATER RESISTANT with no figure means everyday contact only and no swimming. 5 BAR is suitable for sports such as swimming. 10 or 20 BAR is suitable for diving not using an air cylinder.

The SRPD55 is not sold as a diver's watch and Seiko does not claim ISO 6425 for it. The screw case back and the 10 bar figure put it in the swim-and-snorkel class under Seiko's own table, one step below the 20 bar Citizen Promaster BN0150.

Seiko also prints a magnetic resistance figure, 4,800 A/m, which neither Timex nor Citizen publish for the watches in this cluster.

Caliber 4R36: accuracy, reserve and what the manual says

Seiko's product page gives the movement's structure but not its accuracy. The figure is in the manual's specification table, read October 16, 2026:

• Loss or gain: plus 45 to minus 35 seconds a day at normal temperature range, only if worn on the wrist at 5 to 35 degrees C
• Vibrations: 21,600 per hour, 6 per second
• Jewels: 24
• Continuous operating time: approximately 41 hours
• Winding: automatic, with manual winding by crown
• Functions: stop second hand, day and date display

What that accuracy band means against the cluster

Plus 45 to minus 35 seconds a day is the widest band in our cluster. At the limit it is more than five minutes a week. Timex publishes minus 20 to plus 40 seconds a day for the Miyota 8215 in the Marlin; Casio and Citizen publish plus or minus 15 seconds a month for their quartz and solar movements.

Seiko's band is a tolerance, not a typical result. We found no owner-measured figures we could read for this reference on October 16, 2026, and we do not quote estimates from third parties.

The 41-hour reserve means the watch stops after a weekend off the wrist. Hand winding restarts it without shaking, and stop-seconds lets it be set to the second, both features the 4R36 has and the Marlin's 8215 partly shares.

Pricing and availability as of October 2026

Seiko's US product page showed USD 350.00 and seikousa.com showed $350 on October 16, 2026. The US store listed the reference Sold Out with a notify-me option, so the maker's price was not purchasable direct on that date.

Seiko does not mark the figure as MSRP and publishes no price history. Authorized dealers set their own prices; we do not report street prices.

Inside our cluster, $350.00 sits between the Timex Marlin's $299.00 and the Citizen's $450.00, and is 3.2 times the Casio's $110.00, by our editors' arithmetic on the makers' list prices. No link on this page carries a commission; see our disclosure.

Ease of use: what the 4.0 is built from

A 4R36 asks more of the owner than any other movement in the cluster. It must be worn or wound, it stops after about 41 hours, and the day and date need resetting after a stop. Stop-seconds and hand winding make those chores quick, which is why the score is not lower.

The push-pull crown and the three-fold clasp with secure lock and push-button release are both documented. Seiko's bracelet has a three-fold clasp; the sheet does not state whether the end links are solid or hollow or whether the clasp has micro-adjustment, so we do not score those.

The deductions are weight and thickness, which Seiko publishes honestly, and the absence of any quick-release or adjustment feature on the sheet.

Features: what the 4.2 is built from

The SRPD55 publishes more mechanical features than the Timex Marlin: stop-seconds, hand winding, day and date, a rotating bezel, LumiBrite, a display back, 10 bar and a magnetic resistance figure. It has no quartz functions, which the Casio GA2100 lists by the dozen.

The crystal is Hardlex, Seiko's hardened mineral glass. Seiko publishes no hardness figure for it, and the watch does not use sapphire. The Citizen and Casio also use mineral glass; only the Timex uses acrylic.

The score reflects a complete, traditional sports-watch feature set at the price, minus points for the crystal and for the absence of a diver's rating on a watch that looks like one.

Value: what the 3.6 is built from

$350.00 buys a Seiko-made automatic with a full fit sheet, a steel bracelet, a bezel and a three-year warranty. Against the Timex Marlin at $299.00 it adds 50 m of rating, a bezel, a day display and a steel bracelet, for $51 more.

The value deductions: Hardlex at $350, the widest accuracy band in the cluster, the heaviest case, and no owner score on the maker's store to confirm the sheet. The Casio GA2100 at $110.00 is more accurate, lighter and more water resistant on paper; it is not a mechanical, which for this buyer is the point.

The Sold Out status at the US store on the checking date does not change the list price but does mean the $350 figure must be found at a dealer.

Support: what the 4.3 is built from

Seiko USA's limited warranty, read October 16, 2026, runs three years from the date of original purchase for retail purchases made from July 1, 2024. Seiko will adjust or repair a watch defective in material or workmanship, including replacement parts of the movement, case and metal band, at no charge.

Exclusions: watch bands made of anything other than metal, accessories, water damage unless the back is marked water resistant, wear and tear, scratches on case or metal band, and damage from unauthorized repair. Periodic overhauls are charged even inside the warranty period.

The condition that trips buyers: the warranty is valid only if the card is filled in and dated by the authorized Seiko dealer, and photocopies are not honored. Three years beats Casio's and Timex's one year and trails Citizen's five. The SRPD55's steel bracelet is covered, which the Citizen's strap and the Timex's leather are not.

What verified owners report: nothing we could read

Seiko's US product page and the seikousa.com store host no customer reviews. On October 16, 2026 we also tried Reddit's r/Seiko, Amazon, Jomashop, Macy's and Long Island Watch for SRPD55 owner reviews; each page was blocked, returned an error or did not exist at the address we had.

So this review carries no owner score, and we have not borrowed one from search snippets or from a blogger's single-unit account. That is a real gap next to the 226 Casio reviews, 210 Citizen reviews and 144 Timex reviews hosted on those makers' own pages.

When a readable verified-owner source for the SRPD55 appears, this page will add it and note the date. Until then, every claim here is Seiko's, and the owner column is empty.

Limits stated by Seiko

The accuracy band applies only when worn on the wrist at 5 to 35 degrees C. The 10 bar rating is for swimming and diving without an air cylinder, not scuba. The warranty needs a dealer-dated card and excludes non-metal bands and periodic overhauls.

Seiko does not publish the Hardlex hardness, whether the bracelet end links are solid, clasp micro-adjustment, lume duration or a measured accuracy for this reference. We did not find those figures on seikowatches.com or seikousa.com on October 16, 2026, and we do not fill them in.

Alternatives

Choose the Citizen Promaster Diver BN0150-28E if you want 20 bar with a scuba label, solar power, within 15 seconds a month and a five-year warranty, and do not mind 44 mm or $450. Otherwise choose the SRPD55 for a mechanical with a published lug-to-lug.

Choose the Casio G-Shock GA2100-1A1 if you want 200 m, 51 g and $110.00 and do not care about a mechanical movement. Otherwise the Seiko gives you the automatic, the steel and the three-year warranty.

Choose a Timex Marlin Automatic if you want a thinner-looking 40 mm dress automatic for $299.00 and only need 50 m. Otherwise the Seiko's 10 bar, bezel and day display make it the more capable everyday piece. Our published pairings are on the comparison index, including the Seiko against the Marlin.

Bottom line

The SRPD55 is the mechanical in our cluster whose maker tells you everything about the case: 42.5 by 46.0 by 13.4 mm, 170.0 g, 22 mm lugs, 10 bar, 4R36 with 41 hours and a published tolerance of plus 45 to minus 35 seconds a day, for USD 350.00.

What Seiko does not give you is an owner score, and on October 16, 2026 neither could we. Buy it for the published sheet and the three-year warranty, and accept the weight and the drift as the price of the mechanism. Other watches we have read are on the watches topic page.

Frequently asked

Sources

• Seiko US product page, 5 Sports SRPD55 - checked October 16, 2026
• Seiko USA store listing, SRPD55 - checked October 16, 2026
• Seiko instruction manual, calibers 4R35 to 4R72, specifications and water resistant performance - checked October 16, 2026
• Seiko USA limited warranty - checked October 16, 2026

Update history

• October 16, 2026 - First documentation review; figures from seikowatches.com/us-en, seikousa.com, the Seiko 4R-caliber instruction manual and the Seiko USA warranty, checked October 16, 2026. No readable owner-review source found on that date.

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