The 13.56M HC49U is a type of quartz crystal manufactured by YIC (Yangzhou Yichuan Electronic Co). It is a blank quartz crystal with an upper case (HC49U) size, with a frequency of 13.56MHz. It is a miniature package that is widely used in the design of low frequency oscillators in many electronic circuits, such as clocks and timers. It is also known for its stability, accuracy, and low power consumption.