This universal lid transforms your existing mouse housing cage into an oxygen recovery, O2/CO2anesthesia, or CO2 euthanasia chamber. This lid does not have a positive pressure seal and should not be used for volatile anesthesia induction unless it is in a non-recirculating chemical fume hood. Mouse Lid 11.5"x 7.25 part #941442,   Rat Lid 18.5" x 9.75" part # 941445