The CER0307B from CTS Electronic Components is a RF Duplexer with Frequency 3.31 to 3.4 GHz, Band 1 3.39 to 3.4 GHz, Band 2 3.31 to 3.32 GHz, Power 2 to 20 W, Insertion Loss 4 dB. Tags: Ceramic, Surface Mount. More details for CER0307B can be seen below.