Google is testing a new double Product Listing Ads carousel in the mobile search results.  Instead of a regular single carousel, Google is running two individual carousels stacked on top of each other.

Here is what it looks like:

Google is using two of the most popular styles of carousels for this implementation – the first is the regular product view for the PLA carousels.  The second is the “Shop by store” variation that includes multiple different stores for the type of product.

In this example, they did not show any additional ads underneath the carousels.  They went straight into the organic search results.  So advertisers advertising via regular AdWords ads will not get the opportunity to display their ads for this search, which is a fairly competitive one.  Only those in the product listing ads will be displayed at the top of the search results.

But a similar search with only one carousel did show regular AdWords ads underneath:

It doesn’t seem to be very common where Google is showing two carousels instead of just a single one.  It could be in cases where Google shows high engagement with both styles of the PLAs, which triggers the double carousels.