The SRPG57K1 and SRPG59K1 are best compared by wrist footprint, band preference, and calendar display. The SRPG57K1 is the heavier steel-bracelet model with day/date; the SRPG59K1 is shorter lug-to-lug, thinner, lighter, and supplied on silicone, with date only. Collectors and search results often call them the “Monster” and “Baby Tuna,” respectively; Seiko identifies them by reference number and Prospex collection.
Both are automatic Prospex divers rated to 200 m / 660 ft, with a unidirectional rotating bezel and approximately 41 hours of stated power reserve. The SRPG59K1 has a larger listed diameter, but its shorter lug-to-lug measurement means diameter alone does not tell you how either watch will fit.
At a glance
| Feature | SRPG57K1 | SRPG59K1 |
|---|---|---|
| Movement | Seiko 4R36 automatic with manual winding | Seiko 4R35 automatic with manual winding |
| Calendar | Day/date | Date |
| Power reserve | Approximately 41 hours | Approximately 41 hours |
| Jewels | 24 | 23 |
| Diameter | 42.4 mm | 43.2 mm |
| Thickness | 13.4 mm | 12.6 mm |
| Lug to lug | 49.4 mm | 44.0 mm |
| Crystal | Hardlex with magnified glass | Hardlex |
| Water resistance | 200 m / 660 ft diver’s | 200 m / 660 ft diver’s |
| Bezel and case features | Unidirectional rotating bezel; screw-down crown; screw case back | Unidirectional rotating bezel; screw-down crown; screw case back |
| Supplied band | Stainless-steel bracelet | Silicone strap |
| Lug width | 20 mm | 20 mm |
| Weight | 186 g | 104 g |
Specifications are from Seiko’s official SRPG57 and SRPG59K1 product information. Dimensions help compare the models on paper, but wrist shape and personal preference affect fit.
Seiko SRPG57K1: the Antarctica Monster
The Seiko Prospex SRPG57K1 is commonly framed by collectors as the Monster-style model. It measures 42.4 mm in diameter, 49.4 mm lug-to-lug, and 13.4 mm thick. Seiko lists its weight at 186 g and supplies it on a stainless-steel bracelet.
Recommended Free Tools
#1 Best Overall
- 【Compatibility】: The replacement silicone watch strap is compatible with watches that use a standard 20mm spring bar. PLEASE confirm the watch lugs' width before purchasing. Just choose the strap with the appropriate width, and it will fit your watch.
- 【Quick Installation】The quick-release strap has a quick-release function, the quick-release spring bar allows you to change the watch strap in seconds without tools.
- 【High-quality material】: The watch strap is made of high-strength and environmentally friendly silicone rubber with a black matte stainless steel buckle. Simple fashion and durable.
- 【Soft and skin-friendly】: The watch accessory watch straps have no sharp edges, feel soft, are light, flexible to use, and very strong. The bracelet can be washed repeatedly without fading.
- 【Wide Application】: The watch strap for men and women is suitable for creating your unique daily style. Ideal for outdoor sports such as running, fitness, hiking, climbing, camping, fishing, golf and more.
Its longer lug-to-lug span and greater weight distinguish it from the SRPG59K1. The numbers are useful points of comparison, not a guarantee of how it will sit on a particular wrist.
What the SRPG57K1 offers
- Steel bracelet: The supplied band is stainless steel.
- Day-date display: Its 4R36 movement provides day and date.
- Magnified glass: Seiko lists magnified glass with the Hardlex crystal.
- Listed weight: Seiko specifies 186 g.
Choose this reference if you prefer a steel bracelet and want a day display as well as the date. Its listed weight and 49.4 mm lug-to-lug measurement are worth checking against your own preferences and wrist shape.
Seiko SRPG59K1: the Antarctica Baby Tuna
The Seiko Prospex SRPG59K1 is often called the Baby Tuna-style model in collector and search language. Seiko lists a 43.2 mm diameter, 44.0 mm lug-to-lug, 12.6 mm thickness, and 104 g weight. It comes on a silicone strap.
Although its listed diameter is larger than the SRPG57K1’s, it is shorter lug-to-lug and thinner. Those measurements may help buyers comparing wrist footprint, but they do not establish how comfortable it will feel on an individual.
Rank #2
- [22mm Watch Bands] Compatible with Fossil Gen 6/Gen 5E 44mm/Gen 5 Carlyle/Gen 4 Explorist HR/Gen 5 Julianna/Gen 5 Garrett HR/Gen 4/Gen 3/Gen 2 Q
- Compatible with Garmin Instinct/Instinct 2/Instinct Tide/Instinct Tactical/Instinct Solar/Instinct 2 Solar, Compatible with Garmin Vivoactive 4/Venu 2/Venu 3, Compatible with Garmin Forerunner 965/955/945/935/745/265/255/255 Music, Bip 5/GTR 4/GTR 3 Pro/GTR 3/GTR 2/2e/GTR 47mm, Compatible with COROS Pace 3/Apex 2 Pro/Apex Pro/Apex 46mm, Compatible with Pebble, Compatible with Ticwatch, and other watches with 22mm width lugs
- Easy to adjust the length to fit your wrist. Fit 6.0"-8.5" (150mm-215mm) wrist. Made of high quality silicone rubber, skin-friendly. Comfortable and Durable
- Come with Quick Release Pins, easy to install and remove from watch without using tool
- Smart Watch and other accessories Not Included
What the SRPG59K1 offers
- Lower listed weight: Seiko specifies 104 g.
- Shorter lug-to-lug: Its 44.0 mm span is shorter than the SRPG57K1’s 49.4 mm.
- Date display: Its 4R35 movement displays the date, not the day.
- Silicone strap: It is supplied on silicone rather than steel.
The 20 mm lug width is a starting point if considering a replacement strap, not proof that a particular strap or end link will fit. Check compatibility with the specific case before buying.
One collection, two different configurations
Seiko describes the Save the Ocean collection as drawing inspiration from polar oceans and glaciers. An official regional SRPG57K1 description specifically connects its dial to penguins in Antarctica. The Monster and Baby Tuna labels are collector and search shorthand, not the formal names used on Seiko’s product pages.
Seiko’s collection materials discuss marine-conservation activity, but the available research does not establish a model-specific donation amount for either reference. Avoid assuming a particular contribution for an individual watch.
Movement comparison: 4R36 versus 4R35
The main movement difference is the calendar:
- SRPG57K1: Seiko 4R36 automatic with manual winding, day/date, 24 jewels, and approximately 41 hours of power reserve.
- SRPG59K1: Seiko 4R35 automatic with manual winding, date, 23 jewels, and approximately 41 hours of power reserve.
Both have manual winding and approximately the same stated power reserve. Choose between them based on whether you want day/date or date only, rather than assuming a meaningful difference in reserve.
Rank #3
- I was upset when my watch’s band holder broke because I wasn't using my sport watch for long time.Sometimes i didn't want to buy whole new watch band,This kit watch band keeper is a great replacement
- We provide multiple sizes watch strap holder if you aren't sure what size you need. You will receive Six different sizes sturdy, black watch band loops with internal dimensions of 16mm/18mm/20mm/22mm/24mm/26mm
- Are you worried strap retaining rings comes out of the band on occasion ？--Our Bands Keeper Fastener Rings design is Anti-slip. Rubber stop was easy to install. They stretch over existing clasps .Prevent loosening and constraining extra length. Not easy to fall off
- Our replacement watch band comes in a sturdy, clear storage box that opens easily and closes securely.You no longer have to worry about losing the watch band strap loop
- The strap retainer rings is flexible and strong,making it easy to attach to the watch wristband and fits most watches. Whether it's diving or sports，Black is not only stylish,but also works well with various colors of straps
Crystal and legibility
Both references use Hardlex. Seiko lists magnified glass with the SRPG57K1’s Hardlex crystal; the SRPG59K1 is listed with Hardlex. The dossier does not establish a hands-on comparison of their practical viewing differences.
Water resistance and dive-watch features
Seiko lists both models as 200 m / 660 ft diver’s watches, with a unidirectional rotating bezel, screw-down crown, and screw case back. This is the manufacturer’s specification; it does not establish the present water resistance of a used or unserviced watch. Condition and service matter when buying pre-owned.
How to choose between them
Compare lug-to-lug length first, then thickness and diameter; also consider the supplied band and whether you use a day display. The SRPG59K1 has the shorter lug-to-lug measurement and lower listed weight, while the SRPG57K1 has a steel bracelet and day/date. These are specification-based distinctions, not a hands-on comfort verdict.
| If you prioritize | Consider | Reason |
|---|---|---|
| Steel bracelet | SRPG57K1 | Supplied on stainless steel |
| Day and date | SRPG57K1 | Uses the 4R36 |
| Lower listed weight | SRPG59K1 | 104 g versus 186 g |
| Shorter lug-to-lug measurement | SRPG59K1 | 44.0 mm versus 49.4 mm |
| Thinner case | SRPG59K1 | 12.6 mm versus 13.4 mm |
| Silicone strap | SRPG59K1 | Supplied on silicone |
Price, availability, and buying checks
Current street prices, stock, and offers are not established by the official specifications and can vary by market and date. Compare current local listings by exact reference, seller, warranty, and condition rather than relying on a single price figure.
Rank #4
- PACKAGE CONTENTS - You will receive 6 black strap retaining rings with internal dimensions of 18mm/20mm/22mm. Black is not only stylish,but also works well with various colors of straps.
- PREMIUM MATERIAL - The strap rings is made of silicone,a soft rubber-like silicone. It is soft,lightweight,comfortable and withstands friction well. They are durable and can be used for a long time.
- HOW TO CHOOSE SIZE - To better match your watch,measure the width of your strap in millimeters with a ruler and add 1mm. Follow this method to order the perfect size. Suitable for most sports watches.
- EASY TO USE - The strap retainer rings is flexible and strong,making it easy to attach to the watch wristband. Simply stretch/slide it onto the clasp. It only takes a second to change.
- WIDE COMPATIBILITY - The strap retainer rings replacement accessory fits most wristbands or smartwatches. The high quality rubber strap ring holds the end of the strap in place and the classic black strap gives your watch a stylish look.
If buying new, verify the reference number and seller status if warranty and authentication are priorities. For an older or pre-owned watch, check the reference on the watch and paperwork, inspect the bezel and crystal, ask about service history, and review the return policy. A used watch’s actual water resistance depends on its condition and service.
Strap and bracelet considerations
The SRPG57K1 is supplied on a steel bracelet, while the SRPG59K1 comes on silicone. Both official specifications list a 20 mm lug width. That measurement alone does not prove compatibility of a replacement strap, end link, or clasp; check fit for the exact reference before purchase.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Verdict
The SRPG57K1 is the choice to consider for a steel bracelet, day-date display, and higher listed weight. The SRPG59K1 is the choice to consider for a silicone strap, shorter lug-to-lug span, thinner case, and lower listed weight. Neither is universally better: compare the dimensions and display against your own preferences.
FAQ
Which watch has the shorter lug-to-lug measurement?
The SRPG59K1 measures 44.0 mm lug-to-lug; the SRPG57K1 measures 49.4 mm, according to Seiko’s official specifications.
Best Value
- 【22mm Compatible Models】22mm watch bands fit for all traditional watch and smart watch with 22mm width watch lugs,such as Garmin Venu 4 45mm/3 45mm/Venu 2/Vivoactive 4 45mm;Garmin Forerunner 965/955/945/935/745/265/255/255 Music/ 570 47mm;Amazfit T-Rex 3 Pro 48mm; Amazfit Bip 6/5,Balance 2/Balance/Cheetah,GTR 4/GTR 3 Pro/GTR 3; Huawei Watch GT 6 Pro 46mm/GT 6 46mm/GT 5 46mm/5 Pro 46mm;COROS Pace 4/Pace 3/Pace Pro/Apex 4 42mm/Apex 2 Pro; Xiaomi Redmi Watch 5 Active/Lite etc.
- 【Premium Elastic Nylon Material】22mm elastic watch bands are made of premium nylon materials,which is breathable, comfortable, lightweight, durable, and can be washed. 22mm nylon watch bands are suitable for attending different occasions, and also suitable for people of all ages, especially suitable for gifting to family and friends.
- 【Adjustable Size Design】22mm quick release watch bands are equipped with an active adjustable buckle. The adjustable size design allows you to easily adjust the required size without any tools. The adjustable bands fits wrist size is: 5.5in-9.8in (140mm-250mm).
- 【Easy To Install And Use】22mm watch band comes with quick release pins at both ends that lock precisely and securely to your watch. Easy to install and remove in seconds.
- 【Customer Service】If you have any questions about our 22mm elastic nylon watch bands, please contact us at any time, and we will serve you wholeheartedly.
What is the movement difference between the SRPG57K1 and SRPG59K1?
The SRPG57K1 uses the 4R36 with day/date. The SRPG59K1 uses the 4R35 with date only. Both are automatic with manual winding and have an approximately 41-hour stated power reserve.
Are the SRPG57K1 and SRPG59K1 the official Monster and Baby Tuna models?
“Monster” and “Baby Tuna” are collector and search labels used for the comparison. Seiko’s official product pages identify the watches by reference number and Prospex collection.
Do both watches have the same water resistance?
Yes. Seiko lists both at 200 m / 660 ft diver’s water resistance. For a pre-owned watch, actual water resistance depends on its condition and service.
Can I fit any 20 mm strap to either watch?
No. Both specifications list a 20 mm lug width, but that does not confirm that a particular replacement strap, end link, or clasp will fit. Check compatibility with the exact reference.
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.
