The ECS-21K15A 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 1.5 dB, Rejection 35 to 50 dB. Tags: Through Hole, Crystal Filter. More details for ECS-21K15A can be seen below.