Find Your Size

Apple Watch

When ordering a new Apple Watch band or bumper, it's important to know the case size to ensure everything fits your Apple Watch perfectly. Remember, sizing is based on your Apple Watch case size, not your wrist size.

One way to find your case size is by looking on the back of your Apple Watch device. However, the engraving is small and may be hard to read.

The easiest way to find your case size is by opening the Watch app on your iPhone. In the app, select "All Watches" in the top left corner. Then, you can easily verify your case size.


The easiest way to verify which Fitbit model you have is to look at the back or side of the device for the model number. It begins with FB and is followed by three digits. For example, Fitbit Sense has a model number FB512 and Fitbit Versa 3 has a model number FB511.

Here is a complete list of all major Fitbit devices and their model numbers:

Fitbit Model No. Type Release Date
Fitbit Flex FB401 Tracker May 2013
Fitbit Surge FB501 Tracker October 2014
Fitbit Charge FB404 Tracker November 2014
Fitbit Charge HR FB405 Tracker January 2015
Fitbit Blaze FB502 Smartwatch January 2016
Fitbit Alta FB406 Tracker February 2016
Fitbit Charge 2 FB407 Tracker September 2016
Fitbit Flex 2 FB403 Tracker October 2016
Fitbit Alta HR FB408 Tracker March 2017
Fitbit Ionic FB503 Smartwatch September 2017
Fitbit Versa FB504 Smartwatch April 2018
Fitbit Charge 3 FB409 Tracker October 2018
Fitbit Inspire HR FB413 Tracker March 2019
Fitbit Inspire (NON-HR) FB412 Tracker March 2019
Fitbit Versa Lite FB415 Smartwatch March 2019
Fitbit Versa 2 FB507 Smartwatch September 2019
Fitbit Charge 4 FB417 Tracker March 2020
Fitbit Versa 3 FB511 Smartwatch August 2020
Fitbit Sense FB512 Smartwatch September 2020
Fitbit Inspire 2 FB418 Tracker September 2020
Fitbit Charge 5 FB421 Tracker September 2021