The ECS-135.6-20-3X-TR from ECS Inc. International is a RF Quartz Crystal with Frequency 13.56 MHz, Frequency Stability ±50 ppm, Frequency Tolerance ±30 ppm, Load Capacitance 20 pF, Equivalent Series Resistance 60. Tags: Surface Mount. More details for ECS-135.6-20-3X-TR can be seen below.