The ECS-96SMF21A20 from ECS Inc. International is a Band Pass Filter with Frequency 21.39 to 21.41 MHz, Bandwidth 10 kHz, Center Frequency 21.4 MHz, Insertion Loss 2 dB, Rejection 70 dB. Tags: Surface Mount, Crystal Filter. More details for ECS-96SMF21A20 can be seen below.