We have been using these bits for years, they work very well for drilling the through wire hole in your lures or raw blanks. Recommend high speed and if done on a drill press we highly recommend holding the lure or blank with a pair of vise grips or pliers. All of our drilling is done on a high speed custom cnc machine and it's not uncommon to run these bits for several thousand lures before they need sharpening. Larger size will have less error when drilling through a long piece of wood. These work equally well on cedars or hardwoods. Remember to clean your chips every 1-2" for a better drill. Parabolic flutes are 6" long on both size bits with an overall length of 8". Recommend starting the hole with a shorter drill bit to make the hole more accurate also.