DGW......I picked up mine from Millenium Technologies up in WI about 15yrs ago. THey were the shop we used for replating cylinders. THey recommended them over the ball hones on plated cylinders as per their expereince, the ball hones can bounce in/out of ports and potenially chip the edge of the Nikasil. CHecked around and most places seem to carry only the ball/grape/dingleberry hones. Might try grainger or MSC. I have seen some a plumber friend had in his shop that looked the same that they used for cleaning boiler tubes, etc. However I don't know what material or grit they were composed of.