Amazon.com Inc. has developed a new version of its cashierless shopping technology for clothing retailers — in an effort to expand the system beyond convenience and grocery stores.

The retail and cloud-computing giant on Tuesday said the latest iteration of its Just Walk Out technology uses radio frequency identification, or RFID, tags to keep track of apparel.

Previously, Amazon’s system has relied on ceiling-mounted cameras and shelf sensors to determine who grabs what. The technology automatically charges a swiped credit card upon exiting the store. But the system can struggle to distinguish goods that are similar in weight and appearance.

Enter RFID tags, which are affixed to individual items and monitored by fixed readers inside the store. The technology has been around for decades and is primarily used to track inventory and foil shoplifters. Avery Dennison Corp. provided the RFID gear, Amazon said in a blog post.

Amazon has deployed Just Walk Out technology at a few dozen Go convenience stores and Fresh grocery outlets, as well as stores operated by licensees – mostly sports concessions and airport shops. It’s unclear how many apparel retailers will use the RFID version for fear of relying on a fierce rival for crucial in-store technology.

Amazon has quietly piloted its RFID-enabled Just Walk Out technology at fan shops at two Seattle sports arenas: Lumen Field, home of the National Football League’s Seahawks, and Climate Pledge Arena, of the National Hockey League’s Kraken. Amazon Chief Executive Officer Andy Jassy is a minority owner of the hockey team.