Epson offers VCXOs in various package sizes and types, frequency ranges from 1MHz to 800MHz, output types, multiple tolerances and APRs, and voltages from 1.8V to 5.5V. For VCXOs with frequencies above 60MHz, the QMEMS process is once again applied. To increase the frequency of a crystal unit, the crystal chip has to be made thinner using a QMEMS process technology since the degree to which chips could be thinned with conventional processing is limited. QMEMS allows Epson to overcome this limitation by thinning only the area of the chip near the excitation electrode (to create a reverse-mesa structure), thus maintaining the strength of the crystal chip. This allows a desired High Frequency Fundamental (HFF) oscillation to stabilize high-speed, high-volume data transmissions while suppressing nearby high-frequency spurious components (note the orange circles in bottom right figure shown here).