These are the copper findings / end caps and slides  used in my classes. The cone measures 12 x 11 mm;  The filigree end caps measure 10mm; The tube slide matches the filigree cap and allow you to add a pendant to your necklace. 12mm opening should work with size 8 beads or SMALLER.

End caps sold in packs of 2: $4 each set.
Tube Slide: $2 each

Holly’s Tip: Wire wrap several different focal beads onto their OWN  lobster clasp and you will have interchangeable pendants for your kumihimo necklace!  Simply attach to the slide with the lobster!