It is Build 14393.67 that has been pushed to Insiders today. Read More here.

Microsoft may push Windows 10 Mobile Build 14393.51 to Insiders in Fast Ring very soon. The Build as expected brings some fixes and improvements. Since the changelog also has fixes for Windows 10 Mobile issues, it seems it will be out for Mobile devices soon.

Windows 10 Mobile Build 14393.51 Changelog:

This update includes quality improvements and security fixes. No new operating system features are being introduced in this update. Key changes include:
  • Improved reliability for Internet Explorer 11.
  • Addressed issue to keep pen click settings after updating to Windows 10 Version 1607.
  • Addressed issue that may cause Windows 10 Mobile devices to hang after turning Bluetooth on and off very quickly.
  • Security updates to Kernel Mode Drivers, Microsoft Graphics Component, Microsoft Edge, Internet Explorer 11, and Windows Authentication Methods.