Q-Sense E1/E4 use QCM sensor 

                          Frequency：      4.95 MHz +/- 50 kHz
                          Cut：                   AT
                          Electrode layer： 40 nm - 1 μm

                          Size Diameter:     14 mm,                    

                          Thickness:            0.3 mm
                          Finish:                   Optically polished,

                          surface roughness of electrode： less than 3 nm (RMS)

                    Basic elements: Aluminum, Cobolt, Chromium, Copper, Gold, Iron, Iridium,

                    Magnesium, Molybdenum, Nickel, Palladium, Platina, Silica, Silver, Tantalum,

                    Titanium, Tungsten, Zirconium
                    Oxides: Silicon dioxide, rough Silicon dioxide, Aluminium oxide, Iron oxides,

                     Zirconium oxide, Cerium oxide, Zinc oxide, Silver oxide, Magnesium oxide,

                     Titanium dioxide, Indium-tin oxide

                    We have both Titanium/Gold and Chromium/Gold electrodes, we can supply both polished

                    and un-polished.