The ECS-21K12B from ECS Inc. International is a Band Pass Filter with Frequency 21.394 to 21.406 MHz, Bandwidth 6 kHz, Center Frequency 21.4 MHz, Insertion Loss 2.5 dB, Rejection 65 to 70 dB. Tags: Through Hole, Crystal Filter. More details for ECS-21K12B can be seen below.