What is the volume of buffer solution needed in the buffer tray?

You want the solution in the buffer tray to fully cover the specimen tube in order to produce the best results, which means that the buffer tray will be filled to the brim with solution. You will need 210 mL of solution to fill the buffer tray when working with the 20 mm specimen tubes, and 215 mL of solution to fill the buffer tray when working with the 15.5 mm specimen tubes.