The ECS-49-20-18-TR from ECS Inc. International is a RF Quartz Crystal with Frequency 4.9152 MHz, Frequency Stability ±100 ppm, Frequency Tolerance ±30 ppm, Load Capacitance 20 pF, Equivalent Series Resistance 150. Tags: Surface Mount. More details for ECS-49-20-18-TR can be seen below.