Amazon Fresh customers in the Seattle region will be required to become Amazon Prime Fresh members — at a cost of $299/year — to continue using the grocery delivery service after June of next year, the company confirmed this morning.

This brings the Seattle market in line with Amazon’s approach in other cities, where a Prime Fresh membership is already required to use the service.

But it’s a major change for the Amazon customers who served as a test market for Amazon Fresh in the company’s hometown for six years, helping Amazon hone its approach prior to the rollout of Amazon Fresh to cities including L.A., San Francisco and New York.

Customers were notified in email messages this morning that Amazon Fresh in Seattle “will be available exclusively to Amazon Prime members.” But the message did not go into detail about the level of Amazon Prime membership that will be required — potentially leaving the incorrect impression that a standard $99/year Amazon Prime membership would suffice.

In an email exchange with GeekWire this morning, an Amazon spokesperson clarified that a $299/year Amazon Prime Fresh membership will be required to continue using the service after June of next year. The Prime Fresh membership includes all the benefits of a standard Amazon Prime membership, including free two-day shipping on Amazon.com orders.

As part of the change, the company is promising “reduced prices on thousands of Amazon Fresh items.”

Existing standard Amazon Prime members will have their remaining Amazon Prime membership refunded on a pro-rated basis if they opt to upgrade to the Amazon Prime Fresh membership.

In addition, the company tells us that Amazon Fresh customers in the Seattle region will be eligible for a free Amazon Dash device, a handheld gadget that lets customers add items to their grocery list using their voice.

Amazon is also simplifying how it charges for delivery in the Seattle market. Previously, Amazon Fresh customers in Seattle needed to maintain “Big Radish” status — ordering a certain volume over time — to receive a lower minimum order threshold for free deliveries. In its message to customers this morning, the company says all orders over $50 will be delivered for free starting today, eliminating the Big Radish program.

This is the same delivery concept as in other markets, although the minimum threshold elsewhere is $35 per order for free deliveries. We’ve asked Amazon if the Seattle threshold will be reduced to $35, as well, once the Prime Fresh requirement kicks in next year.

Update: Amazon declined to answer the question of what the threshold for free delivery will be in Seattle after June of next year.

Amazon says eligible existing Amazon Fresh customers in Seattle will be able to use the grocery delivery service for the next six months, at no additional charge, regardless of their Amazon Prime status. Standard Amazon Prime members in the Seattle area who start using the Amazon Fresh service on or after today will be able to use it for free through March of next year.