The CER0121C 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, Operating temperature -40 to 85 Degree C. Tags: Ceramic, Surface Mount. More details for CER0121C can be seen below.