The R1901 from Qualcomm is a SAW Resonator with Frequency 315 MHz, Centre Frequency 315 MHz, Insertion Loss 1.4 to 1.8 dB, Capacitance 3.6 pF, Quality Factor Unloaded 7500 to 10600. Tags: Surface Mount, SAW Resonator. More details for R1901 can be seen below.