By purchasing and applying a Tobii Pro Upgrade Key to the consumer eye tracker Tobii Eye Tracker 4C, the device becomes compatible with the Pro SDK. For further details please check the detailed description: https://www.tobiipro.com/siteassets/tobii-pro/product-descriptions/tobii-pro-upgrade-key-product-description.pdf/
For setting up the Tobii Eye Tracker 4C with the upgrade key please check the user instruction: https://www.tobiipro.com/siteassets/tobii-pro/user-manuals/tobii-pro-upgrade-key-user-instructions.pdf/
It is not possible to use other consumer eye tracker (e.g. the Tobii EyeX) with the Tobii Pro SDK.