i can only say that; after just doing no. 8....there were about 30 larger stones..1.5-2 cm....and over 400 tiny to med. size one. this makes about 1400 to date. am hoping to do next one in a week and a half. if i am still putting out this many after 8 times..think what no. 12-20 might do..i will keep doing this until no more stones pass; then continue on w/a maintenance protocal..maybe 3 or 4 times a yr. Keep Flushing those stones away...