This is a 3225-sized, 4-pin Surface Mount Device (SMD) Crystal Resonator manufactured by SJK. It has a RoHS mark and carries the part number 7U36000E20UCG. This type of component is based on a quartz crystal, which produces a highly stable frequency output when energized by an oscillating electric signal. It is used in electronic circuits to keep a stable, accurate timing. It is widely used in radios, cell phones, modems, TVs, and other electronics.