Crystal trim, Swarovski
Attach the trim at the upper edge of a bra cup like this:
Finish the upper edge of the foam cup (lining) by an over-locker or a sewing machine zigzag. Set the ”comb” along the top edge so that the crystal stripe is left outside. Stitch over the plastic teeth.
Set the cup cover on the foam cup right sides against each other, the crystal trim sandwiched between them and the seam allowance on the plastic teeth. Sew in place using zipper foot or similar allowing you to get as close as possible the line of the crystals. Fold the cover down to reveal the beautiful crystal edge!