As you know, Azure Site Recovery (ASR) allows you to replicate your virtual machines (either from on-premise to Azure or between 2 Azure regions) to provide you disaster recovery if your primary site is failing.
If you are using Azure Site Recovery to replicate between 2 Azure regions, when you fail back to your primary region after a fail-over ASR is now able to automatically clean up all deallocated virtual machines and network interfaces created during the failover.
To take advantage of this new capability, you need to have your Azure Virtual Machines running the ASR extension version 9.28.5345.1 or later.