(AP) — Amazon is taking aim at grocery stores and discounters like Wal-Mart with a grocery service that lets its Prime loyalty club members fill up to a 45-pound box with groceries and get it shipped for a flat rate of $5.99.

The mega online retailer says the service, called Prime Pantry, will offer Prime users an expanded selection of items that they usually pick up in grocery stores, in addition to larger in-bulk groceries more commonly ordered online, at competitive prices. Some items now available are single boxes of Cheerios, a six-pack of Bounty paper towels and Coca-Cola fridge packs.

Amazon has been bulking up services for its Prime membership program since it increased the annual membership price to $99 from $79 in March to help offset rising shipping costs.