The SRO20S from Suntsu Electronics Inc is a Rubidium Oscillator with Frequency 10 MHz, Frequency Retrace ±0.02 ppb, Supply Voltage 12 V, Control Voltage 2.5 V, Short Term Stability 0.02 to 0.03 ppb. Tags: Drop-in. More details for SRO20S can be seen below.