So the way that we measure pressure is by taking the ratio of the largest to the smallest. So we have contraction, our cystily 120 and relaxation 80. So it's 120 over 80 is the normal blood pressure. Now, the last thing I'd like to briefly discuss is why there is a pressure difference pressure gradient in the first place. Notice in the arteries, we have a large pressure. In the veins, we have a small pressure.