Typical production AR-15 pins are ~.245" diameter and flat on the ends. They operate in .250 pin holes, and items used to push the pins occasionally slide off and can scratch your lower receiver.
This pin set is ~.248" diameter, allowing you to improve your upper to lower receiver fit, and features early Armalite / early Colt style dimples to assist in location of bullet tips or tools used to push the pins. The tool locating dimples reduce the likelyhood of scratching your lower and add a nice feature to ease diss-assembly.
Note: Some Ar15's are manufactured out of specification and are designed to have no tolerance with .245 pins. These would not be a good candidate for this part. Mil-spec uppers and lowers however typically have .006-.008" of play and these pins will remove ~.002-.003 of that play, improving fit and feel of the parts.