Google seems to be testing a new set of search refinements that let you filter by the brand or specific store you want to filter your results by. So a search for a [camo backpack] has search refinements for colors and size and type but also to let you filter by results on Amazon and Walmart, for example.

When you click on the brand, it will not do a site command, but rather just add the brand name to the search query.

Here is a screen shot of this from Ryan Mews on Twitter who shared a ton of examples – note, I cannot replicate this:

Here are some more:

I kind of like the icon that shows a blue store for the store/brand specific filters.

Forum discussion at Twitter.