The crystal plate inside the TO-8 vacuum holder. Such approach results in radical reduction of the OCXO sizes, power consumption and warm-up time. In spite of very small sizes and extremely low power consumption these oscillators exhibit excellent frequency stability and low phase-noise level comparable with that of the high-end conventional OCXO designs. The MXO37/8UP and MXO37_8UPS (SMD) models have DIP8 compatible sizes and pins-out and are the world smallest high stability OCXOs.