These high speed steel (HSS) bits are great bit for a one time job. While HSS does not typically last as long as solid carbide or carbide tipped they do have a niche in hand fed operations. HSS tools have a small degree of flex in them that allows the tool to be more forgiving versus solid carbide which is more rigid and may break if dropped or abused. These tools are similar to the Onsrud 63-000 series.
Onsrud 40-000 series - 1 Edge Spiral Upcut - High Speed Steel