Ions from the ion transfer tube pass through the RF lens and then the Exit lens. The RF lens is an ion transmission device consisting of progressively spaced, stainless-steel electrodes. The MS applies an RF voltage to the electrodes and the adjacent electrodes have voltages of the opposite phase. The RF potential gently and efficiently guides ions through the first vacuum region. The Exit lens acts as a vacuum baffle between the higher-pressure API source interface region and the lower-pressure MP00 RF rods region of the vacuum manifold. The RF lens and Exit lens mount to the API source interface cage.