The AM4000B1250 from Anatech Electronics is a Band Pass Filter with Frequency 3.95 to 4.05 GHz, Bandwidth 100 MHz, Center Frequency 4000 MHz, Insertion Loss 4 dB, Upper Rejection 40dB @ 3845 MHz. Tags: Ceramic, Surface Mount, Ceramic Filter. More details for AM4000B1250 can be seen below.