In molecular biology, centrifuges are used in procedures involving isolation and purification of proteins and nucleic acids. Often these processes are performed with small, benchtop microcentrifuges which hold multiple 1.5 mL to 2.0 mL tubes and can spin with centrifugal forces as high as 13,000 to 15,000 g. In such experiments, sample tubes of identical weight must be placed in appropriate rotor slots to ensure that the centrifuge is balanced.