Coming soon · Not for sale yet
WatchGearLab
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Coming soon Compatible with Seiko Marinemaster MM300

CB03 Curved End Rubber Compatible with Seiko MM300

CB03 curved-end rubber — Compatible with Seiko Marinemaster MM300. Fill for COROS Sailcloth SKIP; case gap vs CB05/CB04/CB08.

$75.00 Price anchor · not for sale yet
Case Seiko Marinemaster MM300
Color Black
Color Black

Stock: 0 · Not in LIVE catalog · Checkout blocked for this SKU

Draft listing for Owner visual review. Gallery uses peer PDP product photos (logo-scrubbed). Coming soon — not sellable. Draft anchor $75.00 (white-label at peer Crafter Blue CB03 MM300; SKU draft field only; global price policy untouched)

Not sure about fit? Try Fit Finder

Compatible with wording only — not Official OEM
30-Day Returns when this SKU goes live
Free Shipping on US orders $35+

Highlights

  • CB03 curved-end rubber — Compatible with Seiko MM300
  • Curved end rubber strap (select)
  • Independent of CB05 SKX / CB04 Shogun / CB08 Turtle
  • Third-party accessory — competitor trademarks not used in customer copy
  • Black (select)
  • 1-year warranty when the listing goes live

Built for the day

MM300

CB03

MM300

Curve.

End

Rubber

End

Fit.

Daily

Dive

Daily

Wear.

Compatibility

Designed as a third-party accessory. WatchGearLab is not affiliated with the watch brand named for compatibility.

Seiko Marinemaster MM300 (select)Confirm case / lug when liveCurved-end rubber — not a smartwatch band

Exact mold / lug mapping will be verified on sample units before this page goes live.

Materials & Construction

Strap

Rubber (select).

Buckle

Metal buckle finishes (select).

Sizing & Fit

Case

Seiko MM300 when live.

Wrist

Confirm length when live.

Size Chart

Draft guide for Coming soon review. Hole count / magnetic travel and exact wrist ranges will be confirmed on sample units before this SKU goes live. Measure your wrist where the band sits, not over the watch case.

Watch case Select on this page Approx. wrist (mm) Approx. wrist (in)
MM300
CB03		BlackS–MM–L
  1. Check your watch case size in Settings → General → About (or the case back).
  2. Choose the matching case-size pill above.
  3. If you are between lengths, prefer the larger case-size option when available — samples will lock final length.

Not sure? Try Fit Finder. Compatible with Apple Watch only — not Apple Official.

What's Included

  • 1× CB03 curved rubber Compatible with Seiko MM300
  • Fit note (English)

Product photos show a typical concept layout. Final colors may vary within the stated assortment.

Care

·

Rinse after swim; mild soap OK; air dry.

Shipping & Returns

When this SKU launches: free US shipping on orders $35 or more. Standard delivery 5–8 business days. 30-day returns on unused items in original packaging. 1-year limited warranty on manufacturing defects.

Frequently Asked Questions

Is this a Crafter Blue® / Seiko® product?
No. White-label CB03 curved rubber. We do not use Crafter Blue or Seiko trademarks on this listing.
Is it the same as CB05 or CB04?
No. CB03 is curved for Marinemaster MM300 — separate from SKX / Shogun.
Can I buy this today?
Not yet. Coming soon draft — Add to Cart disabled; stock is 0.
What about returns / warranty?
When live: 30-day returns on unused items; 1-year limited warranty on manufacturing defects.

Trademark notice

Seiko Marinemaster MM300 name appears only for compatibility. WatchGearLab is not affiliated with Seiko or Crafter Blue.