ppg and dupont make production clears. dry hard , chip easily and are hell to buff. not to mention they are overpriced. spi is by far a better clear for custom or restoration work . it buffs with ease, stays flexible and resist chips. if your doing collision work it really does not matter what you use . 2 coats and gone. thats what their clears are designed for. spi is designed for guys like us doing custom work. try 6 coats of ppg or dupont clear and see how fast is goes south. i use spi epoxy for sufacing , ppg concept for color , and spi universal clear .