The SiMF4/2-8D3 from Sainty-Tech Communications Limited is a Band Pass Filter with Frequency 3 to 5 GHz, Center Frequency 4 GHz, Insertion Loss 1.2 dB, Rejection 30 dB @2.3GHz&5.65GHz, 40 dB @2GHz&6.75GHz, 60 dB @DC~1.6GHz, 60 dB @8.2~10GHz, Upper Rejection 30 to 60 dB. Tags: Surface Mount, Cavity Filter. More details for SiMF4/2-8D3 can be seen below.