And not secrete means if any of this substance is found in the Ethernet arterial, it is not actually secreted by the peritubular capillaries back into our filter. So case number one freely filtered, not absorbed, not secret. So for a substance X that is freely filtered visaglomerilus, but it is neither reabsorbed nor secreted, what exactly will be our renal clearance. Well, let's take a look at the following diagram. So, we basically have 625 milliliters of blood volume enters this glomerulus every single minute. And every single minute 125 ML/minute is actually cleared.