Bottom line: The Citizen Promaster Mechanical Diver 200m NB6021-17E is a 2022 ISO-rated mechanical diver that combines Citizen’s Caliber 9051, Super Titanium, sapphire crystal and stated Type 2 magnetic resistance. It is a modern Challenge Diver descendant, but it is not the same watch as the older NY0040 family or the larger NB6004-83E. This guide explains what Citizen actually specifies—and what still must be confirmed in your market.
This is a research-based product guide, not a personal wear test. No independent measurements of accuracy, lume duration, bezel action, comfort or water resistance are available here.
What is the Citizen Promaster Mechanical Diver 200m?
Citizen introduced the Mechanical Diver 200m in 2022 as a modern interpretation of its Challenge Diver lineage. The official global collection lists reference NB6021-17E and identifies the line as an “ISO Diver 200m / Magnetic-resistant mechanical movement.” Citizen names Caliber 9051, Super Titanium, sapphire glass, a unidirectional bezel and luminous hands and dial among the watch’s features.
The collection is a current design family, not a reissue of one exact 1970s reference. Citizen says the new model retains the original Challenge Diver’s case diameter while using an improved, thinner case and enhanced magnetic resistance. The complete NB6021-17E dimension set, local price, regional configuration and availability are not stated in the global collection material and should be checked on the Citizen site for your country.
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- VERIFY YOUR WATCH MODEL & MEASURE THE CORRECT SIZE USING A RULER – Watch Parts Are Model and Size Specific. Please Verify Compatibility Before Purchasing.
- Compatible with Multiple Models: Fits Citizen Watch 59-S51866 Eco Promaster and models like BJ2110, BJ2111, BJ2117-01E, BJ2118, BN0085, B740-S067201. Ensure compatibility with your watch before purchase.
- Premium Silicone Rubber: Made from top-quality silicone rubber, this diver strap offers exceptional comfort and durability, surpassing many originals in softness and fit.
- Sized for Comfort: The strap features a 23mm width at the lug and 20mm at the buckle. Length: 13cm (5.1") long side, 8.5cm (3.3") short side. Check dimensions for the best fit.
- Curved End Design: Designed with a curved end for a seamless fit with your watch. The strap enhances the watch's appearance while providing a secure, comfortable wear.
Challenge Diver history and what it does—and does not—prove
Citizen dates the Challenge Diver to 1977. In its official history, the company recounts that a watch found at Long Reef Beach in Sydney in 1983 was heavily covered with barnacles after a long immersion; Citizen says there was no water ingress and that the mechanism was still working. That is a brand-history anecdote, not a controlled modern dive or laboratory test.
Citizen describes the 2022 Mechanical Diver 200m as inheriting the earlier watch’s design cues and “world view.” The historical connection explains the styling, but it should not be used to transfer specifications from an older NY0040 or NY008 reference to NB6021-17E.
Core specifications Citizen publishes
| Feature | NB6021-17E information |
|---|---|
| Movement | Citizen Caliber 9051 automatic mechanical movement |
| Stated diver rating | ISO Diver 200m classification in Citizen’s Mechanical Diver 200m collection |
| Magnetic resistance | JWCA Type 2 requirement, according to Citizen’s stated test condition |
| Case material | Super Titanium |
| Crystal | Sapphire glass; Citizen describes a flat top, domed inner surface and straight-cut sloping sides |
| Bezel | Unidirectional rotating bezel |
| Dial and hands | Luminous hands and dial |
| Case diameter, thickness, lug width | Not stated in the cited global collection material; verify the local NB6021-17E listing |
| Price, stock and warranty | Market-specific details not established; check Citizen and authorized retailers at purchase |
How strong is the magnetic-resistance claim?
Citizen says Caliber 9051 uses anti-magnetic materials in its hairspring and other components. The company states that the watch meets the JWCA Type 2 requirement by maintaining performance when placed 1 cm from a magnetic field of up to 16,000 A/m generated by an ordinary electronic device.
Rank #2
- Iconic Promaster watches with advanced functions designed to venture to the deepest depths.
- 3 Hand, Date
- Silver-Tone Stainless Steel
- Luminous Hands and Markers and Anti-Reflective Mineral Crystal
- Featuring our Eco-Drive technology – powered by light, any light. 200 Meters Water Resistant and 5 Year Limited Warranty
That is a defined resistance claim, not immunity from every magnet or magnetic environment. Phones, speakers, magnetic clasps, induction equipment and industrial sources can differ substantially in field strength and exposure. Treat the figure as Citizen’s stated test condition and follow the manual if the watch is exposed to an unusual field.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsWhat “ISO Diver 200m” means in practice
Citizen’s diver-technology material says its diver watches conform to relevant ISO standards and that a caseback marked “Diver’s Watch 200m” is visible evidence of ISO certification. The Mechanical Diver 200m collection is identified as ISO Diver 200m.
The classification describes the watch as designed and tested to the applicable diver-watch requirements. It is not a promise that an unknown, damaged or improperly serviced example is safe for a particular dive. Follow the instruction manual, inspect seals and have older or serviced watches checked before relying on the rating underwater.
Rank #3
- The strap is made of soft silicone, sweat resistant, waterproof, durable, and comfortable to wear
- The clasp is made of 316L stainless steel needles, which are sturdy and durable
- Compatible with Citizen Promaster diving watches with a 20mm wide strap: BN0150, BN0151, BN0168, NY0121, NY0040, etc. It is also compatible with Seiko diving watches: Monster Mini Turtle、Solar Chrono、Sumo、Alpinist、SBDC031、SKX023、SKX013、MM300、SARB033、MM200
- Packaging includes: This set includes 1 strap, 1 tool, and 3 spring bars
- If you are unsure if your watch is compatible, please contact us and we will reply to you within 24 hours
Materials and design details
Super Titanium case
Citizen describes the case as lightweight and scratch-resistant Super Titanium. The material choice is intended to reduce weight compared with conventional steel while preserving a tool-watch construction. “Scratch-resistant” is a material and treatment description, not a guarantee against marks in daily use.
Sapphire crystal profile
The crystal is sapphire, with Citizen describing it as flat on top, domed inside and straight-cut along sloping sides. Those details belong to the Mechanical Diver 200m collection and should not be assumed for every Promaster or older NY0040 variant.
Controls and legibility
The published feature set includes a unidirectional bezel and luminous hands and dial. No independent timing of lume duration or bezel-action testing is available, so those performance questions remain unverified here.
Rank #4
- Iconic Promaster watches with advanced functions designed to venture to the deepest depths.
- An Eco-Friendly Evolution: Citizen launches first Titanium Watch in 1970. More than 50-year-old evolution of innovative timepieces crafted from proprietary space-age material.
- Benefits of Super Titanium: Lightweight for Better Comfort, Scratch Resistant, Gentle on Skin, and Rust Resistant. Five times harder and 40% lighter than stainless steel.
- Luminous Hands and Markers and Mineral Crystal
- 200 Meters Water Resistant and 5 Year Limited Warranty, ISO Compliant
NB6021-17E versus related Citizen divers
Several Citizen references look related but are materially different products. Keeping the reference numbers attached to their own specifications avoids the most common buying mistake.
| Reference | Published details | Why it is not interchangeable with NB6021-17E |
|---|---|---|
| NB6021-17E | Mechanical Diver 200m collection; Caliber 9051; Super Titanium; sapphire; ISO Diver 200m and magnetic-resistant positioning | Global collection material does not provide the complete dimensions, price or regional configuration |
| NB6004-83E | Automatic titanium diver; Caliber 9051; stated 42-hour power reserve; ISO compliance; 200 m water resistance; Super Titanium bracelet; 46 mm case width | Separate reference with a bracelet and a larger listed case; the U.S. page showed “Sold Out” when accessed, a temporary regional snapshot rather than a global availability statement |
| NY0040 family | Older stainless-steel mechanical diver family with varying movements, bands and regional specifications | Different generation and construction; NY0040 specifications cannot establish NB6021-17E fit or performance |
| NY0105-81E | Asia limited edition: 42 mm case, Caliber 8203 day/date automatic, 200 m water resistance, ISO 6425 compliance, limited to 500 pieces for selected Asian markets | These figures apply only to that specified edition, not to NB6021-17E |
Why NY0040 listings cause confusion
Citizen’s NY0040-09W design archive records a 1997 launch, Caliber 8203 and a stainless-steel case. It describes a rounded caseback and deeply recessed rotating-bezel contours intended to help handling with dive gloves. Those are NY0040-09W details.
A separate Citizen Europe listing for NY0040-09EC specifies Caliber 8204, a 42-hour power reserve, 20 bar water resistance, a 42 mm diameter and a 20 mm urethane strap. Regional references can therefore vary even within the NY0040 family. The 20 mm figure does not prove that a 20 mm replacement strap fits NB6021-17E; confirm the newer watch’s lug width and end-fit first.
Best Value
- Made For Men With Big Wrists – 9.65" Total Length: Finally, a watch band built for larger wrists. At 2 inches longer than standard bands, this triple extra long strap comfortably fits wrists between 7.5" and 9.65" (190mm–245mm), so you never have to deal with a band that's too short to buckle again.
- 20mm Mens Leather Watch Band for Citizen Watches: Compatible with Citizen Watches that use 20mm watch band spring bars. Measure watch lug where watch band and spring bar meet the watch casing. (See Pictures for Instructions on How To Measure). See model list in description to verify if watch is compatible with this watch strap.
- Compatible with Citizen 20mm lug width watch models: CA4420-81L, BM7251-53H, BM7252-51E, AW1607-03H, AW1608-01E, AO9000-06B, AR0070-51A, AR0070-51E, AT0200-05E, AT0709-08E, AT2396-78E, AU1043-00E, AU1044-58E, AW0018-00F, AW1211-12A, AW1231-58B, AW1520-51E, AW1523-01E, AW1593-06X, AW1620-13X, AW1620-21E, AW1620-81E, AW1620-81L, AW5005-12X, BJ6480-51E, BJ6501-10L, BM6835-15E, BM7140-54L, BM7258-62L, BM7354-85A, BM7390-06E, BM7407-81H, BM7460-11E, BM7460-88E, BM7460-88H, BM7463-12A, BM8240-03E
- BM8242-08E, BM8430-59E, BM8434-58A, BM8454-93A, BN0000-04H, BU2026-65H, BV1111-83L, BV1118-84E, CA4455-86X, CA4500-16X, CA4500-83E, CA4505-12E, CA4505-80L, FB1360-54D, FB1362-59P, FB1376-54E, FC0000-59D, BM6814-58E, BL8000-54L, AR3015-53E, AT2340-56A, AW1490-50A, AW1490-50E, BJ6520-82E, BJ6520-82L, CA4405-17H, AP1050-56L, AR1110-11B, AR3078-88E, AT0205-52E, AT0955-01E, AT2390-07A, AT2390-82A, AT2390-82L, AT2393-17H, AT2396-19X, AT2396-86E, AT2437-13E, AT2530-85A, AT2530-85L
- AT2530-85X, AW0077-19L, AW0079-13X, AW0090-11Z, AW0092-07Q, AW1233-01A, AW1670-82A, AW1676-86A, AW7014-53A, BM7494-51L, JP1010-51L, BJ2115-07E, BJ7128-59G, BJ7129-56E, BN0100-26E, BN0159-15X, NB6004-08E, NB6021-17E, NY0084-89E, NY0100-50M, NY0100-50X, NY0125-08W, NY0145-86E, BN5057-00E, BN0162-02X, BN0163-00H, BN0165-55L, BN0166-01L, BN0167-50H, BN0168-06L, NB6021-68L, NB6025-59H, BN0150-28E, BN0151-09L, BN0190-07E, BN0195-54E, CA0715-03E, CA0719-53E, BN0200-05E, NY0040-09E
Buying and ownership checks
Confirm the exact reference
Read the caseback, warranty card and retailer listing together. “Promaster Diver,” “NY0040,” “NB6004” and “NB6021” are not interchangeable search terms.
Verify your market’s listing
Before paying, check the local Citizen product page for dimensions, strap or bracelet configuration, price, warranty language and stock. The global page establishes the collection features, but not every regional specification.
Check condition if buying pre-owned
- Confirm the crown, bezel, crystal and caseback show no damage that could compromise sealing.
- Ask for recent pressure-testing or service documentation rather than relying on the printed 200 m rating alone.
- Verify that the movement and reference match the seller’s description; older NY0040 parts or specifications should not be assumed to be original NB6021-17E equipment.
Be cautious with accessories
A replacement strap should be ordered only after the NB6021-17E lug width and end shape are confirmed. The 20 mm measurement documented for NY0040-09EC is not evidence of compatibility.
Quick Recap
Who should consider it?
- Consider it if you want a modern automatic diver with Citizen’s titanium case, sapphire crystal, stated ISO Diver 200m classification and defined magnetic-resistance claim.
- Look elsewhere if you specifically want the established dimensions, day/date layout or lower-cost parts ecosystem of an NY0040, or the bracelet and 46 mm case listed for NB6004-83E.
- Wait for confirmation if your decision depends on exact case size, strap fit, local price, warranty or immediate stock; those details require a current, market-specific listing.
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.
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