The American phillips drivers have a radius at the root of the four blades, the jis has no radius, goes down to a 90 corner. JIS works good on American screws, but the radius on the American driver keeps it from fully engaging the jis screws. I just ordered a set of long and short hex shank jis bits, $45 ouch. They will work well in my Ryobi battery powered impact driver. Regards, Tom