General Information: 1) G 3171A, HP 5975 Innert MSD Standard-Turbo EI Mainframe for use with 6890GC 2) G 3172A, HP 5975 Inert MSD Perfromance Turb EI Mainframe for use with 6890 GC 3) G 3174A, HP 5975 Inert XL MSD EI/PCI/NCI Mainframe for use with 6890 GC, includes 262 L/sec turbo pump, Inert EI ion source and CI ion source. This used HP 5975 Innert MSD is really in a great shape and tested at SpectraLab Scientific. 90 days warranty included. We are professional to the stuffs. Please call us.