The ECS-21K15B from ECS Inc. International is a Band Pass Filter with Frequency 21.392 to 21.407 MHz, Bandwidth 7.5 kHz, Center Frequency 21.4 MHz, Insertion Loss 2 dB, Rejection 65 to 80 dB. Tags: Through Hole, Crystal Filter. More details for ECS-21K15B can be seen below.