Most changes Amazon makes to its core shopping business are aimed at making its Prime membership program more attractive. One recent change to a key seller policy is accomplishing that by expanding the catalogue of products eligible for Prime two-day shipping.
Known as “seller-fulfilled Prime,” the new program allows businesses that sell goods on Amazon to qualify their products for Prime two-day shipping without warehousing those goods with Amazon. Previously, these businesses had to store goods in Amazon warehouses through a program called Fulfilled by Amazon if they wanted a product to qualify for Prime shipping — something some businesses weren’t comfortable with.
Amazon announced on Tuesday that it had added more than 500,000 products to Prime’s catalogue of 20 million items through this program in the second half of 2015 alone. Re/code first broke news of the beta program last May.
Merchants that participate in the program have to have a good track record of delivering items on time. Amazon doesn’t subsidize the two-day shipping cost for participating sellers, but does allow them to use Amazon rates, according to the company.
For Amazon, the program is the latest example of the company’s focus on packing value into the $99-a-year Prime program, which produces Amazon’s best customers. While the program started with the central perk of unlimited two-day shipping, it has since expanded to include a host of other benefits like free music and video streaming and free two-hour shipping in about 20 cities.
The initiative also helps Amazon artificially expand its warehouse footprint by effectively outsourcing the storage of Prime products to the merchants selling them.
This article originally appeared on Recode.net.