As you can see from my photos, the radius of curvature of these bits is tiny (when rounding 64 inches you get about 1/32", 1/16" and 1/8" radius') and are therefore best suited for dense hardwoods where you can really see small curves, as softwoods vary too much, even with a clean edge, to go from 1/32" or 1/ 16" to benefit radius Use on hardwood is also the reason these bits have four cutting edges.