UPDATE Aug 9 2017
-> made the stronger version, download the one named 'stronger'
This is a Pebble Steel connector / adapter to be used with 22 mm Nato G10 strap. Printed mine in PLA 0.1 mm - 5 wall perimeter (almost solid fill density), strong enough to keep everything together so far.
If you don't know what NATO/G10 strap is, it is a generic strap for any kind of watch. Originally made for the military but now available freely (and cheap!) in many watch shops. Just Google it!
If you printed this, please upload yours, it will be great to see how it works on your pebble steel.