Need to borrow a dress for a Hamptons weekend?

Armarium — the on-demand app that enables women to borrow a selection of current, luxury ready-to-wear and accessories — plans to open a pop-up shop at Baron’s Cove in Sag Harbor from July 22 to July 31. Customers and guests of the hotel can rent an assortment of statement ready-to-wear pieces and accessories, and stylists will also be there to assist clients.

Among the designer looks featured are Missoni cocktail dresses and palazzo pants, Sara Battaglia for Ferragamo clutches, and vintage pieces from LaDoubleJ and Etro, among others.

Baron’s Cove is at 31 West Water Street in Sag Harbor. The shop is open from 10:00 a.m. to 8:00 p.m. daily.

Amarium is headed by Alexandra Lind Rose, who worked in the fashion industry for more than 20 years, and Trisha Gregory, former head of public relations of Salvatore Ferragamo North America.

As reported, normal retail prices for the rtw on the app range from $2,000 to $15,000, and Armarium charges 10 to 15 percent of that to borrow a dress or accessory. The average cost of borrowing rtw is between $450 and $600, and the average cost of borrowing accessories — which include jewelry, gloves, clutches and handbags — is between $200 and $300. All of Armarium’s items can be borrowed when needed, for a four-day period. New brands come in regularly.