Amazon today unveiled its latest initiative to speed up delivery times on millions of items for its growing cadre of Prime members.

The tech giant has quietly built smaller versions of its fulfillment centers closer to customers in Philadelphia, Phoenix, Orlando and Dallas to bolster same-day delivery in those areas. The move represents another way Amazon is pushing the envelope of shipping, in an attempt to get ahead of competitors that are also speeding up delivery times.

The new warehouses allow Amazon to offer more than 3 million items for same-day delivery in those cities. That is a major expansion over Prime Now, the existing same-day service that offers roughly 20,000 items for rapid delivery, along with groceries.

Customers will see a new “Today by” tag on items eligible for same-day delivery. Overnight delivery will be an option as well, with orders placed before midnight arriving by 8 a.m.

Same-Day delivery is free to Prime members on orders over $35. A $2.99 fee will be added on orders under $35. Non-Prime members will have to pay close to $13 for same-day orders.

The new warehouses are about one-tenth the size of Amazon’s typical fulfillment centers that are typically located in more isolated areas. These facilities will help Amazon reduce drive time and air shipping for deliveries, which will bring Amazon closer to a Climate Pledge it made late last year.

“This is because these new facilities are in close proximity to customers, reducing the need for aircraft transport and generally decreasing the distance drivers have to travel to deliver packages to our customers,” Jon Alexander, Amazon’s director of delivery experience,” wrote in a blog post.

Amazon revolutionized the shipping industry in recent years when it pushed for two-day delivery. That soon became the standard across the e-commerce world, with many of Amazon’s competitors adopting a two-day turnaround.

In 2019, Amazon plowed billions into a push to make one-day delivery its new shipping standard for Prime. The move has helped Amazon grow the $119/year Prime program to more than 150 million subscribers.