ABLS-4.000MHZ-B2-T is an HC/49US (AT49) SMD low profile quartz crystal designed for precision timing applications. This 4.000 MHz fundamental mode crystal features a compact package size of 11.5 x 4.7 x 4.2 mm and operates over a temperature range of -20°C to +70°C. It offers a maximum ESR of 180O, frequency tolerance of ±20 ppm at +25°C, and frequency stability of ±50 ppm over the operating temperature range. The crystal is RoHS compliant, hermetically sealed, and suitable for RoHS reflow soldering processes. Common applications include computers, modems, microprocessors, and wireless applications where reliable timing is essential.