The FMFL021 from Fairview Microwave is a Low Pass RF Filter with Frequency DC to 2 GHz, Stopband Frequency 3 to 4 GHz, 3 dB Cutoff Frequency 2000 MHz, Insertion Loss 1 dB, Upper Rejection 40 to 60 dB@3 to 4 GHz. Tags: Module with Connector. More details for FMFL021 can be seen below.