A while ago, I contacted Thorlabs technical support on how to make their Polaris parts UHV rated. They generally rate their parts as 1E-5 rated without a bake out and 1E-9 with "proper bake out". They wrote the following and attached the document attached here

For the suggested Polaris bake out procedure, you can refer to the attached document. This will consist of heating the flight hardware in a clean, certified vacuum system (<1 x 10-5 Torr pressure) at the highest temperature permitted without endangering the hardware but at least 10 degree Celsius ( C ) above its in-flight operating extreme, assuming this temperature does not exceed the maximum exposure temperature. Our non-Piezo Polaris mounts have a maximum operating temp at 200° listed on our website, so we can suggest a bakeout at 210°C. The 8-32 and M4 cap screws included with the Polaris mounts are not rated for pressures below 10^-5 Torr. Prior to placing any components in a sensitive vacuum system, a thorough pre-baking in a bake-out oven should be performed to remove all moisture and surface volatiles.

We can't reach 1E-5 Torr in our vacuum oven, but I still think we should bake out the components at ~1 Torr and 200°C.