Round-head "FR" nails have a full round head which is required by code in some areas of the country. The full round-head has more holding power in high winds and earthquakes than the Clipped head would. The "FR" fasteners collation is plastic, the fastener angle is 22 and the nail shank is offered in a variety of lengths and diameters.
Clipped Head Nails
Clipped head "FC" nails have a "D" shaped head. Each stick holds twice as many nails. The "FC" fastener collation is paper, the angle is 34 and the nail shank is offered in a variety of lengths and diameters.
Note: Check your local building code as some locales require a round-head nail for severe weather locations.