An Adaptation kit upgrade (AKU or Adaptation kit update) updates Microsoft's Windows Mobile operating systems for devices (excluding Windows 10 Mobile).
It is a collection of updates, fixes and enhancements to the tools delivered to hardware device manufacturers to create or update devices based on a specific platform.
This term is used by Microsoft to designate the current update version for a particular embedded platform such as Windows Mobile which is used for personal digital assistants and smartphone devices. On the Windows Mobile platform the AKU is to Windows Mobile what a service pack is to Microsoft Windows.
Microsoft releases AKUs to allow device manufacturers with updates to create new products or fix issues with older products. These enhancements are usually not available to the consumer or end user unless released as a firmware update from the vendor.