Google Inc. appears to be testing a new display for its Product Listing Ads—the listings that show a product’s image, price and the retailer selling it prominently in Google results for product-related searches. In the new format that appears on some searches Google showcases 16 PLAs to consumers on desktops, far more than the usual number.

Google typically presents PLAs in one of two ways to desktop users: It may show a “container” of five PLAs above paid search results or a “container” of eight in the right rail. A consumer can see more PLA results if he clicks on Google’s Shopping tab.

If Google were to start expanding the number PLAs it shows users, it would mean retailers would have to adjust the metrics they use to gauge success with the ad unit, says Link Walls, vice president of product management at ChannelAdvisor Corp. One of Walls’ team members discovered the test.

“If Google starts presenting shoppers with more PLAs, retailers’ click-through rates may decline,” Walls says. Even so, the overall number of clicks may remain the same because consumers will see more retailers’ PLAs that were previously relegated to the Google Shopping page.

PLAs are an increasingly profitable advertising tool for retailers. During the holidays Google Shopping, which mainly consists of sales from clicks on Product Listing Ads on Google search results pages, produced 31.7% more sales for ChannelAdvisor clients than during the 2014 holiday season, ChannelAdvisor says.

Google could not be reached for immediate comment.