Google Merchant Center’s new fast delivery feature enhances product visibility for retailers, offering customers expedited delivery options. This feature incentivizes purchases by reducing basket abandonment rates and increasing visibility through the ‘Get it fast’ filter on Google Search, currently available only in the United States.
Retailers can configure their fast delivery options for Australia, Canada, India, Japan, the UK, and the US. Delivery times range between 1 to 4 days, depending on the country. The feature also allows annotations like ‘Free-of-charge 3-day’ or ‘Get it by [Date]’ for eligible listings.

Read the official help page found by Hana Kobzová: About fast delivery in Merchant Center.