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 says the service, called Prime Pantry, will offer Prime users an expanded selection of items that they usually pick up in , 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.

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