The AM21.4CR187 from Anatech Electronics is a Band Pass Filter with Frequency 21.35 to 21.45 MHz, Bandwidth 0.1 KHz, Center Frequency 21.4 MHz, Insertion Loss 5 dB, Lower Rejection 60 dB at Fc +/-200 kHz. Tags: Surface Mount, Crystal Filter. More details for AM21.4CR187 can be seen below.