Garmin Venu SQ watch strap keeper
This is the "keeper" * portion of the watch strap for a Garmin Venu SQ watch, though it will probably fit most watches with a 20mm strap. My original one broke so I printed this one out of TPU. It's much stronger and also a slightly tighter fit to ensure it keeps the loose end of your watch strap in place. Still quite comfortable to wear. Printed at 0.12mm layer height, no supports needed.
*I had to look that up myself, now you know