6 Stone Holder For Work Sharp Professional Precision Adjust6" Stone Holder for Professional Precision Adjust allows using any 6" sharpening stones including Venev Centaur and Venev Ursa Series dual side diamonds, and any Edge Pro form factor stones (with mounting). Note. It's very important to keep a sharpening angle consistent. The angle should not change when progressing to a next stone. If the thickness changes, the sharpening angle changes. Unchecked, this can ruin your sharpening. Use a digital angle