The CER0121A from CTS Electronic Components is a RF Duplexer with Frequency 1.92 to 2.17 GHz, Band 1 2.11 to 2.17 GHz, Band 2 1.92 to 1.98 GHz, Power 5 W, Insertion Loss 1.5 dB. Tags: Ceramic, Surface Mount. More details for CER0121A can be seen below.