These self-feeding Lewis pattern machine auger bits from FAMAG are absolutely superb quality, with a special low friction coating in the spiral to ensure an unimpeded flow of chips away from the working face. Perfect for boring deep accurate holes in softwoods, you do need to use a fairly meaty drill with these (corded type) if you want to use a cordless for this type of work we recommend using the non self-feeding FAMAG 3491 long series bits.