Models 5418 and 5424 include standard aerosol-tight rotors that hold 18 or 24 microcentrifuge tubes, respectively. Lids are designed for optimized airflow and reduced noise levels (practically down to background level). Operation is quiet even for runs that do not use the rotor lid. Additional optional rotors for Model 5424 include a 4 × 8-tube PCR strip rotor and 18 × miniprep spin column/filter rotor.