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, on watch adapters matching its 20mm lug width. The Fitbit Charge 5 and 6 adapters are in the box. The Prospex sits on top of the wrist; the Charge sits underneath, against the skin. Google does not certify readings taken in this position.
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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, on watch adapters matching its 20mm lug width. The Fitbit Charge 5 and 6 adapters are in the box. The Prospex sits on top of the wrist; the Charge sits underneath, against the skin. Google does not certify readings taken in this position.
Seiko Prospex SPB143 lug width
20mm
Fitbit Charge compatibility
Charge 5 / 6
Adapter
Fitbit Charge adapters in the box
Sensor position
Underneath the wrist

Why practical divers pair the Prospex SPB143 with Fitbit Charge

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

Compatible
Yes. The Seiko Prospex SPB143 is compatible with Smartlet One, on watch adapters matching its 20mm lug width. The Fitbit Charge 5 and 6 adapters are in the box. The Prospex sits on top of the wrist; the Charge sits underneath, against the skin. Google does not certify readings taken in this position.
Seiko Prospex SPB143 lug width
20mm Supported
Watch adapters in the lug holes
Fitbit Charge model
Charge 5 / 6
Fitbit Charge adapters in the box
Sensor position
Underneath the wrist
Not certified by Google in this position
Reversible
Fully
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
→

Choose your Smartlet

Step by step

Replace your strap
01

Replace your strap

The watch adapters seat in your mechanical watch's lug holes in place of the spring bars. Classic, Shadow or Titanium. The spring bar tool is in the box.

Connect your wearable
02

Connect your wearable

Your smartwatch attaches to the central part of the bracelet with its own adapter (Apple Watch, Whoop, Fitbit, Galaxy or Pixel Watch) or a pair of standard watch adapters. Zero modification to the mechanical watch.

Wear both simultaneously
03

Wear both simultaneously

Both watches sit on the same wrist. The smartwatch sits underneath, against the skin; readings taken there are not certified by its manufacturer.

Questions

Frequently asked questions

  • Which Prospex references work with Smartlet?
    References with 20mm / 21mm / 22mm lug widths are covered, with watch adapters in the matching width. The Prospex SPB143 model guide lists every reference.
  • Does the Charge track workouts properly on the inner wrist?
    The sensors face the skin underneath the wrist, and the bracelet is sized by its links so the Fitbit Charge sits snug. Google does not certify readings taken in this position: for a reading with medical weight, put the Fitbit Charge back on its own band and follow Google's instructions. Notifications and the other functions work as usual.
  • Does Smartlet affect the Prospex's water resistance?
    No. Smartlet replaces only the strap: the watch adapters seat in the lug holes in place of the spring bars. The case, crown and bezel are untouched, and their ratings are unchanged.
  • Does Smartlet damage or modify my mechanical watch?
    No. The watch adapters seat in your watch's lug holes in place of the spring bars. Nothing is modified on the case, lugs or dial, and the change is fully reversible: your mechanical watch can go back on its original strap at any time.