Amazon.com is making its Same-Day Delivery program even faster. Prime members in Philadelphia, Phoenix, Orlando, and Dallas are offered faster Same-Day Delivery—from click to doorstep in just a few hours.

Up to 3 million items across dozens of categories that are marked “Today by” can now be ordered for delivery throughout the day. Prime members can also order as late as midnight and have their orders on their doorstep the next morning before heading out for the day by selecting the “Overnight by 8am” delivery option. If an Amazon customer selects to have their order delivered overnight, drivers will arrive between 4:30am-8am, which is noted on the product detail page and again at checkout.

The initiative underscores the company’s aim to stay quick in online retail, outdoing competitors’ free two-day delivery offers so shoppers remain loyal to Amazon’s shipping and media-streaming club Prime, which costs $119 per year in the United States.

Amazon has long offered one or two-hour delivery via Prime Now, a service that includes fresh groceries and more than 20,000 items.

The same-day offer will now guarantee delivery of more than 100,000 products, from phone chargers to dog food, in as little as five hours, from a new warehouse close to each launch city. For comparison, Amazon offers more than 100 million items for two-day U.S. delivery or faster via Prime.

The new format combines the storage, picking and packing functions of Amazon’s fulfillment centers with the sorting and delivery functions of other facilities into a single building.

Compared with fulfillment centers, which are farther from urban cores and house much more inventory, the new warehouse is roughly a tenth the size, at 100,000 square feet.

The new facilities are automated with the same ‘drive units’ used in Amazon’s fulfillment centers. These are floor-scurrying robots that hoist up movable shelves of inventory and bring them to associates who pick customer orders.

While the same-day option is covered for Prime members who spend at least $35, those without Prime are charged $12.98 per order.