The ECS-040-18-5PX-JES-TR from ECS Inc. International is a RF Quartz Crystal with Frequency 4 MHz, Frequency Stability ±50 ppm, Frequency Tolerance ±20 ppm, Load Capacitance 18 pF, Equivalent Series Resistance 150. Tags: Surface Mount. More details for ECS-040-18-5PX-JES-TR can be seen below.