500 grains,
I know Cobus the designer of the Impala bullets very well. They are not only designsd for small to medium animals or for brain shots. Their uniquiness lies in the rings on the shaft. If you shoot a animal in the lungs the air "explodes in the lungs and cause a hell of a lot of damage. I know of 2 buffs that was hunted in Zim with a 375 and a 458. Apperently only one shot was needed on every buff. If you want more info on excactly how the bullets perform Cobus will give you all the details.

My experience with the Impalas are very good, after a lung shot there is nothing left of the lungs, the lungs turned in to a blooby pulp every time and the animals expire very quickly. A added benifit is that the meat damage are minimal.