The B138MB1S from Knowles is a Band Pass Filter with Frequency 13.25 to 14.25 GHz, Bandwidth 1000 MHz, Center Frequency 13.75 GHz, Insertion Loss 2.75 to 3 dB, Rejection 40 to 45 dB. Tags: Surface Mount, Ceramic Filter. More details for B138MB1S can be seen below.