All Amazon Prime customers in the US can now set which day of the week they want to receive their packages. Customers can set which day they want as their default delivery day for future packages, and change them at checkout later. Items will come bundled in one package, saving boxes and making shipment deliveries more predictable.

The feature, called Amazon Day, was first introduced in November as an invite-only program. The concept is part of Amazon’s “Shipment Zero” sustainability initiative, which aims to make all of Amazon’s shipments carbon neutral, with half its shipments being carbon neutral by 2030. Amazon says that since testing began with a group of Prime members last year, the company has reduced packaging by “tens of thousands of boxes.”

Amazon Prime members can also use Prime one-day, two-day, and no-rush shipping options. Customers can also choose not to bundle items into an Amazon Day package, and just receive a shipment separately as normal.