Amazon.com Inc. is shutting down all 87 of its U.S. pop-up stores, ending the retailer’s yearslong experiment with these small shops as the company tinkers with an evolving bricks-and-mortar strategy.

“After much review, we came to the decision to discontinue our pop-up kiosk program,” an Amazon spokeswoman confirmed to The Wall Street Journal.

The closings are expected by the end of next month, some employees at Amazon pop-up stores said.

These shops typically occupy a few hundred square feet of space and showcase devices like voice-assistant speakers, tablets and Kindle e-readers. They feature staff, dressed casually in black Amazon T-shirts, who encourage passersby to sample the newest products. Pop-ups are operated in locations ranging from malls and Kohl’s stores to Amazon’s Whole Foods stores in 21 states.

Amazon is expanding its bookstores as well as its so-called 4-star stores, which sell products rated four stars or higher by Amazon customers, “where we provide a more comprehensive customer experience and broader selection,” the spokeswoman said. “We look forward to opening additional locations of both stores this year.”