The BWLF-4 from Sainty-Tech Communications Limited is a Low Pass RF Filter with Frequency DC to 4 GHz, 3 dB Cutoff Frequency 4 GHz, Insertion Loss 1.7 dB @4.0GHz, Rejection 20 dB @6.6GHz, 40 dB @8.5GHz, Power 30 dBm. Tags: Die. More details for BWLF-4 can be seen below.