Which nozzle should be inserted into the machine? The rule is that the size of your cells of interest should not exceed one-fifth of the nozzle diameter. Cells that deviate from an ideal spheroid shape are more susceptible to shear induced damage and cell death. If you have a small cell, switching to the larger (85um nozzle) often results in better viability. Nozzle size guideline: 5-10um = 70um nozzle, 11-16um = 85um nozzle & >16um = 100um nozzle.