The FN-1804W from Filtronetics is a Band Stop Filter with Insertion Loss 2 dB, Rejection 3 to 30 dB, Center Frequency 120 MHz, Ripple 0.5 dB, Operating_Temperature 10 to 35 Degree C. Tags: Module with Connectors, Surface Mount, Drop-in. More details for FN-1804W can be seen below.