Every Month first Monday Google will release its security patch update to its Nexus and Pixel devices. Same way Google released its October security patches available to the devices it supports directly. The factory images and full OTA zip files are available for grabs from the official website. Over-the-air rollout of the update is already underway and it will be available in phases.
If you have a Pixel or Pixel XL, your build number after updating will be OPR1.170623.027 if you’re in Canada or on Project Fi, and OPR3.170623.008 for everyone else. The Pixel C gets OPR1.170623.027, Nexus 6P has OPR5.170623.007, while the Nexus 5X is receiving OPR4.170623.009. The Verizon Nexus 6 has NGI77B as the build number, while other units get N6F27M. The Nexus 9 has two – N4F27P for the LTE model, and N9F27M for the Wi-Fi only iteration.