I've found the CTI OCXOs really impressive for the cost.
The 2 main things that separate them from more expensive OCXOs are:
unpredictable retrace (can restabilise at up to 5 ppb from where they stabilised before) as well as severe frequency drifts over the first 12-24 hours, gradually stabilising over the next few days.
High temperature coefficient (the one I've best characterised has a -500 μHz/K coefficient).
Once stabilised, the performance is very impressive, however.
Here are 2 examples of stability against my reference of another free-running OCXO, a trimble 73090 off aliexpress. This also gives excellent performance and this particular one is in a thermally isolated box and has been running for months, and shows essentially zero aging against GPS.
One is with the OSC5A2B free running, and the other is with EFC temperature compensation.
Note to the eagle eyed - the TC does not appear to be -500 μHz/K, but that is because the ambient temperature is plotted, not oscillator enclosure temperature. Because the OCXO is temperature controlled, it has a stabilising effect on the temperature in the enclosure, typically reducing temperature swing amplitude it by about 50% compared to ambient.