PH Cloud CarDAV Sync is a CardDAV client for Windows to synchronize people (contacts) application from any CardDAV compatible server (Owncloud, Synology, Sabre etc). Due to its implementation as sync adapter it integrates seamlessly with the native people app.
The application is tested with standard protocol RFC6352. Because there are many DAV server implementations you should test with your server using the free trial before you purchase.
Please note that it does not sync with Google & Apple iCloud, since those are already covered from Windows OS accounts.