Well, the collecting duct is involved in reabsorption, and we'll see what it reabsorbs in just a moment. So, under normal conditions, in the absence of any type of hormone, the collecting duct is impermeable to water. And that means no water is reabsorbed or secreted into our collecting duct. However, under normal conditions, it is slightly permeable to sodium ions. And sodium ions will be reabsorbed by our cells back into the surrounding tissue around our collecting duct, known as the interstituum. So about 5% of the total sodium ions inside the filtrate will be reabsorbed back into our body in the collecting duct.