The listing, Three Black Onyx Stones for Jewlery has ended.
From left to right in the photo, below are the specs:
1) 16mm x 14mm, 5.3 carats
2) 4.7 carats, 14mm x 10mm
3) 2.5 carats, 12mm x 10mm
These seem to be calibrated for putting in jewelery link rings or something.