Seiko Prospex SPB143 & Fitbit Charge on the same wrist

Seiko Prospex SPB143 & Fitbit Charge on the same wrist

Yes. The Seiko Prospex SPB143 is compatible with Smartlet One, with the Fitbit Charge adapter included in the box. The Prospex mounts via its 20mm / 21mm / 22mm lug width; the Charge sits on the inner wrist with full skin contact and full tracking.
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Compatibility guide

Seiko Prospex SPB143 & Fitbit Charge on the same wrist

Seiko Prospex SPB143 + Fitbit Charge
Yes. The Seiko Prospex SPB143 is compatible with Smartlet One, with the Fitbit Charge adapter included in the box. The Prospex mounts via its 20mm / 21mm / 22mm lug width; the Charge sits on the inner wrist with full skin contact and full tracking.
Seiko Prospex SPB143 lug width
20mm / 21mm / 22mm
Fitbit Charge compatibility
Charge 5 / 6
Adapter
Adapter included in every Smartlet box
Sensor accuracy
Fully maintained

Why practical divers pair the Prospex SPB143 with Fitbit Charge

Liquid error (sections/compat-combo-section line 172): metafield_tag can only be used with a metafield drop

Is the Seiko Prospex SPB143 compatible with Fitbit Charge on Smartlet?

Compatible
Yes. The Seiko Prospex SPB143 is compatible with Smartlet One, with the Fitbit Charge adapter included in the box. The Prospex mounts via its 20mm / 21mm / 22mm lug width; the Charge sits on the inner wrist with full skin contact and full tracking.
Seiko Prospex SPB143 lug width
20mm / 21mm / 22mm Supported
Standard spring-bar system
Fitbit Charge model
Charge 5 / 6
Adapter included in every Smartlet box
Sensor accuracy
Fully maintained
Inner wrist position
Reversible
In seconds
No modification to the watch

Related compatibility guides

Model guide
Seiko Prospex SPB143
→
Brand guide
All Seiko models
→
Smartwatch guide
Fitbit Charge compatibility
→

More ways to wear Smartlet

Seiko 5 + Fitbit Charge
Seiko 5
→
Hamilton Khaki Field + Fitbit Charge
Hamilton Khaki Field
→

Step by step

Replace your strap
01

Replace your strap

Smartlet replaces your mechanical watch strap via the standard spring-bar system. Classic, Shadow, or Titanium. No tools required.

Connect your wearable
02

Connect your wearable

Smartlet uses a dedicated adapter or native lug pins depending on your smartwatch. The connector snaps onto the Smartlet module. Zero modification to the mechanical watch.

Wear both simultaneously
03

Wear both simultaneously

Both watches sit on the same wrist. All smartwatch sensors maintain direct skin contact and operate normally.

Questions

Frequently asked questions

  • Which Prospex references work with Smartlet?
    References across 20mm / 21mm / 22mm lug widths are covered via the standard spring-bar system; the Prospex SPB143 model guide lists every reference.
  • Does the Charge track workouts properly on the inner wrist?
    Yes. The inner-wrist position preserves constant skin contact, so heart rate, steps, and sleep tracking operate normally.
  • Does Smartlet affect the Prospex's water resistance?
    No. Smartlet replaces only the strap via the spring bars. Case, crown, and bezel are untouched, and their ratings unchanged.
  • Does Smartlet damage or modify my mechanical watch?
    No. Smartlet replaces your standard watch strap using the existing spring-bar system. It makes no permanent modification to the watch case, lugs, or dial. The process is fully reversible in seconds. Your mechanical watch is unaffected and can be worn independently at any time by reinstalling its original strap. Smartlet is engineered to watchmaker tolerances and tested with the same care that goes into the watches it pairs with.