NEW YORK (AP) — Amazon is increasingly claiming territory once held exclusively by department stores and it's doing so again, essentially placing a dressing room in your house.

Amazon is testing a new service for Prime members that allows them to try on the latest styles before they buy at no upfront charge. Customers have seven days to decide what they like and only pay for what they keep. Shipments arrive in a re-sealable box with a pre-paid label for returns.

Amazon said Tuesday that more than a million pieces of clothing and accessories are eligible and include brands like of Calvin Klein, Hugo Boss, Theory and Levi's. Shoppers receive discounts depending on how much they keep.

The Prime Wardrobe service is the latest move by Amazon into fashion and could be another big blow to department stores. It's also attacking Walmart, which has been snapping up clothing brands including ModCloth and the latest Bonobos as tries to snare millennials from Amazon and others.

Amazon has made a big push to expand its offerings under private labels like Lark & Ro designed to be as stylish as recognizable national brands. Prime Wardrobe could keep Prime members from straying.

Amazon is poised to surpass Macy's this year as the largest U.S. clothing seller, according to Cowen & Co. analysts. The industry observer expects Amazon's share of the U.S. clothing market will increase from 6.6 percent last year to 16.2 percent by 2021.

Prime Wardrobe works this way: Shoppers pick three or more items and then have a try-on period to find the best styles. For items they want to discard, customers can drop off at a UPS location or schedule a free pick up. Shoppers will receive 10 percent off if they keep three or four items or 20 percent off for five items or more.

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