The 501-27512-81 from Quantic Wenzel (Wenzel Associates, Inc.) is a OCXO with Frequency 100 MHz, Supply Voltage 15 V, Phase Noise -125 dBm/Hz@100 Hz to -95 dBm/Hz@10 Hz, Phase Noise 1 kHz -150 dBm/Hz, Phase Noise 10 kHz -165 dBm/Hz. Tags: PCB Mount. More details for 501-27512-81 can be seen below.