Switch over if you've still got the old 3mm allen hex screws.
Much better than the terrible M4 3mm allex hex bolts that came originally with the older c-260 stems. These bolts are harder, and don't round off after 2 tightening cycles. I recommend anyone who's still got the original 3mm hex bolts to switch over, as the 10 dollars here will save you a lot of time and trouble down the line if the heads round off the next time you make an adjustment.