Bullseye Cell Counting Kits contain cell counting tubes that hold up to 1 ml of cell suspension, and can be centrifuged to pellet the cells into a graduated 5 µl capillary at the bottom of the tube. The volume occupied by the cell pellet after centrifugation is called the Packed Cell Volume (PCV). The PCV can then be converted to a useful value such as PCV% or and actual cell number.