Silver metal rectangular ring 25mm.
The ring can be used with the adjuster to make a cross body bag strap adjustable!
https://www.owlandsewingcat.com/products/metal-rectangle-adjuster-size-25mm-used-for-the-3-way-bag
The 3 way bag pattern can be found here - https://www.owlandsewingcat.com/products/three-way-bag-pattern