The BSF-3700MS1 from RF ONE Electronics is a Band Stop Filter with Stopband Frequency 3.6 to 3.8 GHz, Insertion Loss 2.5 dB, Rejection 55 dB, Power 20 W, Return Loss 8 dB. Tags: Module with Connectors, Cavity Filter, Ceramic Filter, LC Filter. More details for BSF-3700MS1 can be seen below.