I bought this set of indexable milling cutters for 304L stainless steel. I want to use extra round inserts to cut a portion of the board down to 1/2" thickness, with concave edges, mostly for looks. On my first test cut, both inserts tore badly. The cut started with a smooth finish, but after about an inch into the cut it became rough and only a small amount was removed from the surface. Both inserts crumble the same way so they hold up well with the tool. I bought new earbuds from another company and they work better now Original inserts may work well for some other materials.