The ECS-400-20-30B-DU from ECS Inc. International is a RF Quartz Crystal with Frequency 40 MHz, Frequency Stability ±100 ppm, Frequency Tolerance ±30 ppm, Load Capacitance 20 pF, Equivalent Series Resistance 30. Tags: Surface Mount. More details for ECS-400-20-30B-DU can be seen below.