A Propagation Site is a small area within one of our Propagation Trays (cMPT). Each tray can hold (2) standard sheets of growing medium that measure 10 x 20. The number of Propagation Sites per tray is dependent on the growing medium used. For example, if you are using Oasis 1 thin cut, each 10 x 20 flat has 276 cells. Each tray holes two sheets or 552 Propagation Sites.